Background: I spent five years at an MBB firm and have since coached a few dozen people through McKinsey loops (both consulting and tech tracks). This is what I've consistently seen matter in the behavioral round.
First, the questions themselves. McKinsey's behavioral questions cluster around a few themes:
Leadership and influence: 'Tell me about a time you led a team through an ambiguous problem.' 'Describe a situation where you had to align stakeholders who disagreed.' These are about showing structured thinking AND emotional intelligence, not just what you did.
Data-driven decisions: 'Walk me through a time you changed course based on data or evidence.' They want to see that you can hold your own hypothesis lightly. This matters a lot for tech roles because McKinsey is genuinely trying to build engineering culture, not just import bodies.
Client/stakeholder impact: 'Tell me about a time your work directly changed how someone made a decision.' On the tech track, 'client' can mean internal stakeholders, product teams, consultants using your platform.
Personal growth / failure: 'What's the biggest professional mistake you've made and what did you learn?' This one trips people up because they either give a fake answer (the weakness that's secretly a strength) or they go too dark. Middle ground: real mistake, real consequence, concrete learning.
Format: they use structured STAR but expect a tighter narrative than most places. Your 'Situation' should be one or two sentences. They will cut you off if you spend four minutes setting context. The 'Action' is where they spend most attention.
McKinsey values they consistently signal: intellectual curiosity, respect for client confidentiality and ethics, entrepreneurial drive. Authenticity over polish. I've seen people fail the behavioral with a very polished, coached answer that rang hollow and pass with a rougher answer that was clearly real.
If I had to pick one prep move: write out three or four stories that you know cold and can adapt to different questions. You need the shape of the story memorized, not the words.