The interviewers want to hear about your greatest weakness as a project manager to see that you are self-aware and can identify an area that needs improvement. When you admit you have a deficiency in a particular aspect of your profession and take steps to improve, it shows the interviewers that you are motivated and inspired to grow professionally.

Focus on a weakness related to your profession, but not one that is an essential job duty. For example, suppose you say your weakness is your verbal communication skills. In that case, the interviewers may pass you over for another candidate since that skill is essential to being an excellent project manager.