How to Handle Employee Complaints About Other Employees?

When one employee complains about another, handling employee complaints about other employees well means acting the day you learn about it: sit down with the person who raised the concern, document what they tell you, gather evidence before word spreads, interview the accused and any witnesses, protect the complainant from retaliation, and impose discipline that fits what you find. The steps below walk through that process and flag the legal rules that shape each one.

Why Moving Quickly Matters

The moment an employee complains, the organization is on notice, and your response starts building either a defense or a liability. For harassment by a co-worker, an employer is liable if it knew or should have known about the conduct and failed to take immediate corrective action.¹

When the accused is a supervisor, the standard is stricter. The employer is automatically liable if the harassment led to a concrete job action such as termination, demotion, or a pay cut. Absent that, the employer can defend itself only by showing it took reasonable steps to prevent and correct harassment and that the complaining employee unreasonably failed to use the company’s complaint process.¹ A prompt, documented investigation is the raw material of that defense.

The Intake Conversation

Start by meeting with the employee who raised the concern. Your goal is to collect enough detail to determine the nature and scope of the complaint. Document:

When each incident occurred, as specifically as the employee can recall.
Where in the workplace it took place.
The name of the accused employee and any witnesses who were present.
The exact words spoken or actions taken, not characterizations like “he was rude.”
How the conduct affected the employee’s ability to do their job.

Listen for whether the complaint touches a legally protected characteristic. Title VII of the Civil Rights Act covers race, color, religion, sex (including pregnancy, sexual orientation, and gender identity), and national origin.² The Americans with Disabilities Act protects employees with physical or mental disabilities,³ and the Age Discrimination in Employment Act covers workers 40 and older.⁴

Employees rarely use legal terminology. Someone who says “my coworker keeps making comments about my accent” is describing potential national-origin harassment even without ever using that phrase. Listen for the substance.

What You Can and Can’t Promise About Confidentiality

Tell the complainant, and later every witness and the accused, to keep the investigation confidential while it is ongoing. The National Labor Relations Board has ruled that confidentiality rules limited to open investigations are generally lawful, because protecting investigation integrity and encouraging honest reporting outweigh the modest impact on employees’ rights to discuss workplace conditions.⁵

Employees can still discuss the underlying workplace events with coworkers. What they cannot share is information they learned or provided during the investigation itself. Once the investigation closes, extending confidentiality requirements becomes harder to justify unless there is a specific concern such as witness safety.

You also cannot guarantee full confidentiality to the complainant. A fair investigation requires sharing enough detail with the accused for them to respond meaningfully. Say so at intake, so the employee understands the process.

Gathering Evidence Before Anyone Else Knows

Before you interview the accused or witnesses, collect the physical and electronic evidence that could support or contradict the complaint. Gathering first lets you ask more targeted questions and reduces the risk that evidence disappears once people learn an investigation is underway.

Pull the personnel files for both employees. Look for prior complaints, disciplinary actions, or performance issues that may reveal a pattern. Review your employee handbook and any written policies that govern the alleged conduct: these set the standard for what your organization treats as a violation.

Preserve relevant emails, chat messages, and text exchanges between the parties. Check whether surveillance footage, electronic badge access logs, or phone records can confirm or disprove where people were at key times. If your organization uses workplace communication platforms, export the relevant conversations before anyone can delete them. Recent performance reviews and prior incident reports can also provide context for the professional relationship between the two employees.

Running the Investigation

The investigation follows a structured sequence: interview the accused, then witnesses, then circle back if new information surfaces. Document every interview in writing, capturing both the questions asked and the responses given.

Interviewing the Accused

Meet with the accused employee, explain the allegations in enough detail that they can respond, and give them a genuine chance to tell their side. Avoid revealing the complainant’s identity if you can, though in many cases the accused will piece it together from the facts. Record their responses during the meeting rather than relying on memory afterward.

Interviewing Witnesses

Interview each witness separately. Ask open-ended questions about what they personally saw or heard, not what they heard from others. Share only what is necessary to get useful answers. Direct observation is worth more than office gossip.

Assessing Credibility When Accounts Conflict

Weigh each person’s testimony using consistent factors. Consider whether the witness is speaking from personal experience or repeating something secondhand, whether they are stating facts or offering conclusions, and whether they have any reason to be biased, such as a close friendship with one party, a grudge, or a personal stake in the outcome.⁶ Try to corroborate disputed claims with electronic evidence or other witnesses before deciding which version is more credible.

If a new name or incident surfaces mid-investigation, go back to the relevant parties and ask about it. The investigation is not complete until every lead has been explored and the testimony reconciles with the physical and electronic evidence.

Union Representation Rights

If your workplace is unionized, employees have the right to request a union representative during any investigatory interview they reasonably believe could lead to discipline. This right, established by the Supreme Court, applies only when the employee asks; you do not have to offer it proactively.⁷ If the employee insists on representation and none is available, you can either wait for one or proceed without that interview, but you cannot discipline the employee for making the request.⁸ The right does not extend to non-union employees under current federal law.

Keeping the Parties Safely Apart

While the investigation is underway, you may need to separate the two employees. The governing principle: any interim measure should not penalize the person who filed the complaint. Transferring the accused to a different shift, reassigning their workspace, or adjusting reporting lines is generally safer than moving the complainant.

Moving the complaining employee to a less desirable position, shift, or location can look like retaliation even when intended as protection. In extreme cases, making working conditions worse for a complainant could amount to constructive discharge, where the employee feels forced to resign because of the employer’s response.⁹ If you must separate the parties, the burden of inconvenience should fall on the accused unless the complainant specifically prefers otherwise.¹

Preventing Retaliation

Retaliation is the single most common type of charge filed with the EEOC, and it can convert a defensible investigation into a costly lawsuit. Federal law prohibits employers from taking any adverse action against an employee because they filed a complaint, participated in an investigation, or opposed conduct they reasonably believed was discriminatory.¹⁰

Retaliation reaches well beyond firing. Actions courts and the EEOC have found retaliatory include giving someone a worse schedule, excluding them from meetings or training, increasing scrutiny of their work without justification, issuing a negative performance review not supported by actual performance, and even threatening consequences against a close family member.¹¹

Build these steps into every investigation:

Remind the complainant, the accused, all witnesses, and their supervisors of your anti-retaliation policy at the outset.
If the accused is a manager or supervisor, coach them on separating their feelings about the complaint from day-to-day decisions.
Have an HR professional or other designated reviewer sign off on any employment action affecting the complainant or witnesses while the matter is pending: discipline, schedule changes, transfers, evaluations.
Check in with the complainant and witnesses periodically to ask whether they have experienced any negative treatment since the complaint was filed.

The EEOC recommends building these steps into your standard protocol so they happen automatically rather than depending on any individual’s judgment.¹²

Reaching a Finding and Taking Action

Once the investigation is complete, review the evidence and reach a conclusion based on a preponderance of the evidence: did the alleged conduct more likely than not occur? Write a report that lays out what you found, explains which testimony and evidence you relied on, and states whether a policy or legal violation occurred. If you weighted certain evidence more heavily, explain why.

If the complaint is sustained, corrective action should be proportional. For a first-time, relatively minor offense, a formal warning and counseling may be enough. For severe or repeated harassment, suspension or termination may be appropriate. The EEOC advises that discipline should be designed to stop the harassment, correct its effects on the victim, and prevent recurrence.¹

Discipline alone rarely finishes the job. Think about what the complainant needs to be made whole: restoring leave they took to avoid the harasser, removing an undeserved negative evaluation from their file, or monitoring the workplace to make sure the conduct does not resume.

Notify both parties of the outcome in writing. The complainant should know that you found the conduct occurred (or did not) and that you have taken action. You do not need to share the specific discipline imposed on the accused, and doing so can raise privacy concerns.

Records You Need to Keep

Federal regulations require employers to keep personnel and employment records for at least one year from the date the record was made or the personnel action occurred, whichever is later. If an employee was involuntarily terminated, records must be kept for one year from the termination date.¹³

If an employee files a discrimination charge with the EEOC or brings a lawsuit, the retention period changes: preserve all personnel records relevant to the charge until the matter is fully resolved, however long that takes.¹³ Store completed investigation files securely, with access limited to those who need it. One year is the federal floor; many employment attorneys recommend keeping investigation files for at least three years given the possibility of delayed claims.

Complaints That Don’t Involve a Protected Characteristic

Not every complaint triggers federal anti-discrimination law. An employee who says a coworker is rude, disorganized, or difficult is describing a personality conflict, not discrimination. Federal law does not require employers to investigate or remedy general workplace unpleasantness. For harassment to be illegal, it must be based on a protected characteristic and severe or frequent enough that a reasonable person would find the work environment abusive.¹⁴

Ignoring those complaints is still poor practice. Unresolved conflicts escalate, and what starts as general rudeness can drift into conduct that does target a protected characteristic. Many employers route every complaint through the same intake process regardless of whether a protected category is involved, which builds a consistent record of accountability and catches problems before they turn into legal risk.

1
U.S. Equal Employment Opportunity Commission. Enforcement Guidance on Vicarious Liability for Unlawful Harassment by Supervisors
2
eCFR. 29 CFR Part 1606 – Guidelines on Discrimination Because of National Origin
3
ADA.gov. Introduction to the Americans with Disabilities Act
4
U.S. Equal Employment Opportunity Commission. Age Discrimination
5
National Labor Relations Board. Board Approves Greater Confidentiality in Workplace Investigations
6
U.S. Equal Employment Opportunity Commission. Chapter 6 – Development of Impartial and Appropriate Factual Records
7
Justia U.S. Supreme Court Center. NLRB v. J. Weingarten, Inc., 420 U.S. 251 (1975)
8
National Labor Relations Board. Interfering with Employee Rights – Section 7 and 8(a)(1)
9
U.S. Equal Employment Opportunity Commission. CM-612 Discharge/Discipline
10
Office of the Law Revision Counsel. 42 U.S. Code 2000e-3 – Other Unlawful Employment Practices
11
U.S. Equal Employment Opportunity Commission. Questions and Answers – Enforcement Guidance on Retaliation and Related Issues
12
U.S. Equal Employment Opportunity Commission. Enforcement Guidance on Retaliation and Related Issues
13
eCFR. 29 CFR Part 1602 Subpart C – Recordkeeping by Employers
14
U.S. Equal Employment Opportunity Commission. Small Business Fact Sheet – Harassment in the Workplace