If you work with someone who constantly oversteps his role and bosses other employees, including his own supervisor, his actions can erode employee morale and hinder job performance. If you want to curb his behavior, you must set firm boundaries and make it clear that you won’t allow him to tyrannize the office.

Understand His Perspective

Putting yourself in your co-worker’s shoes can help you understand his motivation and determine the best way to put a stop to his domineering ways. Watch for patterns in his behavior. Is he always bossy or does he primarily act out when under stress? You may realize he’s insecure because he’s the youngest person at the company or the newest employee and feels the need to prove himself. Or you may discover he’s worse when he’s had a bad meeting with a client or when he’s lost a project or assignment to another employee.

Gather Strength in Numbers

If your colleague dominates the entire workplace, banding together can take away his power. Talk to your co-workers about the situation and its negative effect on the team. Encourage them to stand up for themselves when he starts ordering them around, and tell them you’ll do the same. If even a few people refuse to let the bossy co-worker take control, others may soon follow. It’s also important to approach your boss. If she lets him give her orders, this signals to other employees he has more power than she does. Describe how this behavior hurts the team and ask her to stand up to him on behalf of the staff.

Set Limits

If you argue with your colleague or justify your own behavior, you suggest to him and to others that he has authority over you. When he attempts to order you around, keep your response short and simple. For example, tell him “I can’t take on this project for you because I have too much work of my own.” Or, say “I’ve got everything under control and don’t need any assistance.” Immediately go back to your work and diplomatically refuse to engage him.

Confront Him as a Last Resort

Extreme cases may require a direct approach. Speak privately with him and explain that his behavior puts you in a difficult position because you were hired to report to the boss, not to him. Explain how his bossiness interferes with your productivity and hurts your credibility in the eyes of clients and colleagues. Tell him that you’re capable of managing your work and your time for yourself and ask him to focus on his own job instead of making yours more difficult.