Writing a Complaint Letter Against a Coworker [Free Sample]

Cooperating and getting along with one’s co-workers is important and makes for a good and supportive work environment. However, sometimes this is not possible, especially when you’re working with a difficult co-worker.

Keep In Mind

Keep in mind; one of the best ways to deal with a difficult co-worker is to talk with that co-worker. 

However, if your co-worker has a volatile personality, you may have more success by writing a complaint letter to your boss.

First Step – Define The Problem

To do this with a complaint letter, first define the problem. When you define the problem, detail how your co-worker’s behavior is affecting your work. Do not describe him or her on a personal level.

Instead, if he or she is constantly late for work, describe how you have to pick up the slack. In addition, if he or she is making ethnic or racial remarks to you and is violating the company’s anti-bullying policies, describe this in the letter.

Second Step – Begin The Letter

Begin the letter by writing something like, “I’m writing this letter to report a conflict I am currently having with employee, Lisa Watkins.” 

Continue writing something like, “Because of several incidents that have occurred between her and me, I feel that it is time to make an official complaint.”

Then, write about what happened between you and the co-worker. List each incident separately and with the respective dates.

For example, “On Feb. 11, 2022 I spoke to Lisa about her loud talking and laughing, which interrupted my phone conversation with two of my clients.

Since that time, she has repeated this behavior on five additional occasions.” At this point in the letter, provide the dates for all occurrences.

Third Step – Explain The Bad Behavior

The third step is to write about how this person has affected your ability to work. For example, you could write, “Because of Lisa’s aforementioned behavior, I have had to put my clients on hold several times to ask her to be quiet.”

Then in your letter, state your job duties and your goal to meet them; however, your co-worker’s actions are keeping your from fulfilling your objective. 

Also, state that since you have failed to resolve this issue with her, you would appreciate your manager speaking to her about the issue. Then, thank your boss for understanding.

Final Step – Speak To Manager

The final step would be to see your manager professionally and explain the situation. Continue to say that you have written a letter, which has the details in the letter. 

Give him or her letter. If he or she fails to resolve the issue, go to your human resources department and give HR a copy of the letter.

Here is an example of a complaint letter:

Sample Complaint Letter Against A Coworker

Your Name
Your Address
City, State, Zip Code
Phone Number


Name of Employer
Name of Company
Address of Company
City, State, Zip Code

Dear Name of Employer:

I would like to report a conflict that has arisen between me and [Name of Coworker], my fellow colleague, in the Finance department.

There have been several incidents over the last three months, and I feel that it is time to present a formal complaint.

I would like to report the occurrences on record as follows:

On [Date], the aforementioned coworker and I disagreed about how she disrupted a phone call I was having with a client.

She was laughing and talking out loud; even though I explained to her several times that I couldn’t hear my client on the phone.

The phone call was disrupted and my client did not call back to substantiate a deal that was in process.

Even though I explained to her several times that I couldn’t hear my client on the phone, Lisa continued to talk even louder.

[Name of Coworker], has continued to talk and laugh loudly when I am on the phone with clients.

Because she continues to do this, I am unable to do my job as I should and I am losing clients.

I have felt harassed and belittled by [Name of Coworker] and have suffered stress and verbal abuse on many occasions; not only on [Date] but also five times in [Month] of this year.

The dates in [Month] are: [Date] around one in the afternoon, [Date] at 11am, [Date] at noon, [Date] at 1pm and [Date] at 9am.

I understand that it takes two people to have a conflict and that I may have been responsible for reacting too strongly to her; however, I am actively seeking a decision now.

I would like to suggest that either [Name of Coworker] or I be assigned to different departments or projects or that a mediation session be set up with a third person present.

I feel that I am a loyal and hardworking employee but the stress of this situation has brought on unwanted anxiety about coming to work and has made my work almost impossible. I would like to resolve this issue as soon as possible.

Thank you for your time and understanding.


Your Signature
Your Printed Name

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