Went through the HubSpot loop for a senior PM role a few weeks ago (declined offer, different reasons). Sharing my behavioral prep notes because I spent a lot of time on this and they were pretty accurate.
HubSpot is unusually explicit about their culture code. If you haven't read the "Culture Code" deck they published, go read it before your first interview. Interviewers literally reference it. The values that came up most in my five behavioral rounds:
HEART values (HubSpot's framework) Humble. "Tell me about a time you were wrong about something important." Empathetic. "How do you think about your internal stakeholders' needs vs your users' needs?" Adaptable. "Tell me about a time the roadmap changed significantly under you." Remarkable. Their bar is high here. They want evidence you've driven something notable, not just maintained. Transparent. "Tell me about a time you had to deliver bad news to leadership."
I got variations of all five across my rounds. They're not subtle about it.
Questions I was actually asked (paraphrased) "Tell me about a product you shipped that failed. What did you do differently after?" "How do you handle it when a stakeholder wants a feature that conflicts with your product strategy?" "What's a time you had to influence without authority?" "Tell me about a time you had to make a decision with very limited data."
The last one came up in two separate rounds, which tells me they really care about it.
What they're looking for in answers
They respond well to structured STAR answers but get impatient if you spend 90 seconds on setup and 20 seconds on result. Flip that ratio. They want to hear your reasoning and the actual outcome, not the backstory.
One thing that caught me off guard: a couple interviewers pushed back on my answers. Not aggressively, but with "why did you do X instead of Y?" Make sure you actually know your own stories well enough to defend them. I fumbled one because I'd half-borrowed a story from a team situation and couldn't fully own the decisions.