I've been a first time manager that had a team of former peers and promoted people from IC to manager where their teams were comprised of former peers. This is the advice I provided to the people getting promoted most recently:

Taking a management role where your new direct reports are your former peers is one of the hardest transitions you will make in your career. If you approach it deliberately and with humility, it can also become one of the most rewarding chapters of your professional life.

The first dynamic you should expect is that at least one person on the team will feel they were just as qualified for the promotion as you were. These are rarely low performers. In fact, they are often strong contributors who reasonably believed they were on the same trajectory. I have been on both sides of this situation, and I have also been the person making the decision when only some of several qualified individuals could be promoted. How you handle the people who were passed over matters more than almost anything else you do early on.

Resist the urge to over explain or immediately justify the decision. Give them space to process the outcome and come to you when they are ready. When that conversation happens, be prepared for hard and sometimes emotional questions. This is not a debate to be won. It is an opportunity to listen, acknowledge disappointment, and communicate your intent as a manager. Be clear about how you want to run the team, what you value, and how your promotion does not limit their future growth. If you do nothing else, make sure they leave the conversation believing that your success and their success are not in conflict.

A second challenge is redefining relationships. You are no longer one of the group in the same way you were before, and pretending otherwise will create confusion. This does not mean becoming distant or formal overnight, but it does mean setting consistent boundaries. You cannot selectively remain a peer with some people and a manager with others. Consistency is what earns trust, even when it feels uncomfortable.

Early on, it is tempting to prove that you deserve the role by doing the work yourself. This is a mistake. Your value is no longer measured by individual output but by how well the team performs. Focus on clarity, prioritization, and removing obstacles rather than being the smartest person in the room. Your former peers will notice quickly whether you are enabling their success or competing with them.

It is also important to reset expectations explicitly. Have one on one conversations with each team member early. Ask what is working, what is not, and what they need from you. Share what you expect from them as well. This creates a clean starting point and avoids carrying forward unspoken assumptions from when you were peers.

Finally, accept that not everyone will be happy, at least initially. Some relationships may change permanently, and that is not always a reflection of your performance. Your goal is not to be liked. It is to be fair, transparent, and supportive while making decisions in the best interest of the team and the organization. Over time, credibility comes from follow through, not from trying to make everyone comfortable.