I went through PIMCO's behavioral round about six weeks ago. Coming back after a career gap so I actually prepped harder for behavioral than for technical, and I'm glad I did because the behavioral portion at PIMCO is more structured and more weighted than I expected from a tech interview.
The behavioral was a 45-minute session with the hiring manager. She had a list in front of her and was clearly working through specific competencies. Not freeform conversation.
Questions she asked (paraphrasing): Tell me about a time you worked on a project where the requirements were ambiguous. How did you drive clarity? Describe a situation where you had to deliver difficult feedback to a peer or cross-functional partner. What was the outcome? Tell me about a time when you disagreed with a technical decision made by your team. How did you handle it? Walk me through a project you're most proud of. What would you do differently with what you know now? Have you ever had to work on a time-sensitive deliverable where things didn't go as planned? What did you do?
There was also a question specifically about working with non-engineering stakeholders, which I think reflects PIMCO's environment. You're building tools that portfolio managers and traders actually use. The manager made it clear they want engineers who can communicate clearly to people who don't care about the implementation.
What they seem to value: Ownership and follow-through are a real theme. Several questions circled back to what happened after you delivered something, not just what you built. They also want intellectual humility. The question about what you'd do differently felt like a test for self-awareness, not a trap.
Culture felt more formally professional than a startup but not stiff. The manager was genuinely warm during the conversation.
For prep: I used STAR format for everything but kept it conversational. The interviewers at PIMCO don't seem to want a formal recitation. They want a story that sounds like how a real person actually experienced something.