I've helped maybe 40-50 people prep for Deloitte specifically over the last few years. and I went through it myself. here's how I'd approach it if I were starting from scratch today.
first, understand which practice you're interviewing for. Deloitte is not one interview. Strategy & Operations, Human Capital, Technology, Risk Advisory, and Government Services all have different weightings of behavioral vs. case vs. technical. if you're interviewing for Technology, you might not get a traditional case at all. if you're in S&O, expect a structured case with at least one ambiguous nonprofit or operations scenario.
for behavioral prep:
Deloitte uses a competency-based framework. the competencies they're actually evaluating are: leadership, collaboration, analytical problem-solving, communication, and results orientation. those five things. map your best 6-8 STAR stories to those competencies before you walk in. most people just prep generic stories; mapping them lets you respond to almost anything they throw at you.
the behavioral questions I see most often at Deloitte: tell me about a time you led a team through a difficult change describe a situation where you had to influence without authority when have you had to deliver a difficult message to a client or stakeholder? tell me about a project that didn't go as planned and what you did
for the case:
start with 10 cases from Victor Cheng's Case Interview Secrets or the IGotAnOffer platform, then do 10 partner-led mocks. Deloitte cases in 2026 skew toward organizational transformation, healthcare cost reduction, and public sector efficiency. less pure market entry than you'd get at Bain.
one thing most people skip: research the specific practice you're interviewing for. Deloitte's website is actually useful here. knowing what they're actually working on signals that you made a deliberate choice to be there, not just that you applied broadly.