Hi there,
This is a very common concern and an important one to get right for the PEI. It is not a problem to draw from the same environment or manager, as long as the stories showcase different skills and challenges. Diversity of experience is nice to have, but diversity of skills is what really matters.
How different should your stories be
McKinsey does not expect you to have a completely new environment, manager, or context for every interview. What they do expect is that you show a range of skills and situations. For example, if you use one story to demonstrate leadership, another should ideally demonstrate personal impact or entrepreneurial drive. The interviewer should feel that you have depth in more than one dimension.
Reusing the same environment
It is absolutely fine if more than one of your stories comes from the same workplace, project, or even the same manager. Consultants know that most candidates draw their strongest experiences from one or two roles. What matters more is that the situation, challenge, and actions are distinct. If one story is about leading a team under pressure and another is about convincing a senior stakeholder in the same project, that is perfectly acceptable.
What to avoid
The risk is when stories start to sound repetitive. If all of your examples are from one internship with the same context and very similar challenges, interviewers might wonder how broad your experience really is. To avoid this, frame each story differently and make sure the problem you highlight is clearly unique.
Best practice
Prepare at least two to three strong stories for each PEI dimension. Rotate them across rounds so that you do not repeat the exact same example. If multiple stories come from the same environment, emphasize different angles: in one case your leadership style, in another your problem-solving, in another your resilience.
If you want, I can help you stress test your PEI stories, refine the framing, and make sure you are not repeating yourself across rounds.