Recruiter put me in the process for IB Associate in WB in London. 1st round was a 30-min video call with HR. Next round was a 1-hour interview with a VP (behavioural + technical). Next round was a take-home 2.5hr case study (Teaser+3-statement+Profile review). Next round was 2 separate interviews with the team's Directors. Last round would be meeting the MDs.

Networking call with Senior IB employee who submitted a referral. (no other networking) Then got invited to 1st round zoom interview (30 minutes) which consisted of mostly behavioral and fit questions. Had some basic EV/valuation questions but nothing crazy. Superday was 4 30 min zooms with a break. MD, VP, VP, Associate. One all about LBO (was hard but if you do paper lbo practice questions you will be fine). One was case study and fit questions. MD call was all fit and why Tech. Very much tech focused call. One call was strictly behavioral and scenario based questions (guy joined 15 mins late and we flew through like 20 questions -- was not a lot of fun).

Had coffee chats with a recruiter in the Chicago office and was connected to a partner / MD in their Boston office where I had a great call with him and was able to earn a referral from him where I then heard back about a first round interview in late January

Initial Contact & Application
I applied online through William Blair's careers portal (williamblair.com/ibcareers). Within 48 hours of submitting, I received an automated email with a link to complete the Suited assessment — a personality/cognitive pre-screening tool. There's no real way to prep for it; it tests judgment and soft skills more than finance knowledge. I'd advise not overthinking it, just answer authentically. Make sure to check your spam folder since the link sometimes lands there.
Roughly two to three weeks after submitting, I received an email to schedule my first round interview. I had done some light networking beforehand — I'd connected with a couple of analysts on LinkedIn who were responsive and friendly, which I think helped signal genuine interest.
First Round Interview
A 30-minute Zoom with a second-year analyst (in some cases a VP or Director, depending on office). The format was roughly half behavioral, half technical.
Behavioral questions included the standard: tell me about yourself, why investment banking, why William Blair specifically, and something not on your resume. They go fairly deep on "why Blair" — you need a real answer about the independent partnership structure, culture of accountability, boutique deal exposure, or a specific group you're interested in. Vague answers don't fly here.
Technical questions included: walk me through a DCF, enterprise value vs. equity value, and most importantly — a paper LBO. The paper LBO is a defining feature of Blair's interview process and comes up at almost every stage. Know it cold. Be able to walk through entry/exit, debt paydown, IRR calculation, and key value drivers verbally and on paper without hesitation.
I got a superday invitation about two hours after the first round ended, which was a great sign.
Superday
Four back-to-back 30-minute interviews, all one-on-one. The interviewers were mostly MDs and Directors, with one Associate.
Round 1 (MD) — Behavioral + mini case study. Started with TMAY. Then they presented a brief business scenario and asked me to think through it — somewhat consulting-flavored but they tied it to M&A, asking about comparable transactions and what kind of buyer would be interested. Stay calm and structured.
Round 2 (MD) — Resume-based + markets. Heavy on "why Blair, why this office, why this group." Also asked about an industry I follow, a company I find interesting, what differentiates it competitively, and what the key risks are. Know a sector cold — ideally one relevant to Blair's coverage areas (healthcare, tech, industrials, consumer).
Round 3 (MD) — Pure behavioral. Be ready for situational/ethical questions like: "What would you do if you caught a mistake in a pitchbook the night before a client presentation?" They want to see judgment, teamwork instincts, and maturity under pressure.
Round 4 (Associate) — LBO focused. This is where they really stress-test technical depth. They gave me the paper LBO in parts, almost like a guided walkthrough, but pushed back on assumptions and asked about key drivers of IRR improvement (debt paydown, multiple expansion, EBITDA growth). Know your LBO levers inside and out.

first round was 30min with a mix of behav and technicals, they focus a lot on LBO. and superday was 4 back to back with 2 case-study, one pure LBO, and another one more liek a market analysis, depends on your interviewer. mine was less beahev.

Cold-applied for the Chicago office, no networking. They offered me a first round interview about a month later. Pretty standard first round with an associate, about half behaviorals and half techs. Behaviorals were TMAY, why IB/WB specifically, something not on your resume. Techs were about the LBO, which I messed up a bit but he was super kind and tried to walk me through it until I got it right. Got a invite to the Superday about two hours after the first-round. Superday consisted of four 30 min one-on-one interviews. One was on markets, where they asked abt an industry I was interested in, a company in that industry and what kind of differentiates them but also what the risks are. The next was all behaviorals, have your stories ready but they also ask some "what would you do" questions where like another analyst puts wrong numbers in a pitchbook the night before a presentation and your MD tells you that some of the numbers are probably wrong. After that was kind of a case study about a plant-based meat company, kind of consulting focused but they had a question abt precedent transactions in there. Finally was the paper LBO which they give to you in parts and in a way that kind of makes you think about it. All my interviewers were super nice people and incredibly chill, all my interviews started with TMAY and the LBO guy asked me about my hobbies after I finished. Really liked the people I talked to and I got a call from one of my interviewers with the offer about two hours after the Superday. Overall great vibes and positive experience.

I applied online for the generalist position and also networked with someone in the Technology group in the NYC office at William Blair. After speaking with him, it became clear that they were viewing me primarily as a Technology NYC candidate, which was later confirmed in my first-round interview. Overall, networking was straightforward and very useful for crafting a strong “Why Blair.”

The first round was roughly 50% technical and 50% conversational. Almost all of the technical questions could be found in the basic sections of the M&I 400 guide. The most challenging portion was a “simple” paper LBO. You don’t need to build a full grid—just assume steady free cash flows throughout the holding period—but you should be very comfortable with LBO mechanics, as they do extensive work with PE firms. The remainder of the interview felt very conversational and could be treated similarly to a networking call.

I received the final-round invitation three days later and was given several interview time options (I chose the latest). The final round consisted of four 30-minute virtual interviews over Teams.

The first interview focused on walking through my resume and discussing the current state of the Technology sector, particularly software.

The second was a very open-ended case study. You should be prepared to think through business valuation and risks in a consulting-style framework.

The third interview was another paper LBO, this time slightly more complex. (Be prepared to know what debt amortization is, and that unlevered FCF to levered FCF is different)

The final interview was entirely behavioral and fairly standard.

Each interview included about 5–10 minutes for questions, so it’s important to have multiple backup questions prepared. I received a call with the offer roughly two hours after completing the final interview, and the offer letter was sent immediately afterward.

First Round: 30 minute zoom with a second-year analyst. Mix of behavioral and technical.
Superday was 4 rounds with Paper LBO & case study. Mostly Behavioral

First round was with a director and an analyst. Half behavioral, half technical. Behaviorals were as follows and a few more: Why Blair? Why Chicago? Why IB? What has been the most impactful experience that has shaped your long term career goals in the last 2 years (they go very deep into this)? Technicals: Enterprise value questions, paper LBO, walk me through a DCF/three statements. Got the superday notification 30 minutes after the first round. Superday was 4 30 minute interviews. First was behavioral and a case study with an MD. Second was all resume-based and market-based with an MD. Third was purely behavioral with an MD and had some weird behaviorals. Fourth was all LBO focused with an Associate--know paper LBOs and LBO drivers back and forth. Got the offer call 3 hours after the interview (they wait this long for everyone).
General advice:WHY BLAIR–
Last private firm on the street, which creates less downward pressure on firm leadership, which shapes the firms collaborative culture
Upwards of 70% client retention rate because they act in the best interest of their clients since they are a private firm and are not held accountable to generate x amount of fees per quarter
Work with family/founder owned businesses 50% of the time, so you will be helping these founders/families with their lives work as a junior banker, which is super rewarding
People!! Mention any specific conversations that resonated with you
Headquarted in Chicago – youre at the center of everything and have access to firm leadership as a junior, which is invaluable
MM is going to see boom in next 5 or so years (theres a ton of articles/videos about why)
Chicago!! Just be very clear you only want to be in chicago (super easy if you are from Chicago)
Just have your tell me about yourself down, because this is the first question they always ask
It’s an incredibly conversational interview – they’re legit just screening for fit and making sure that you’re normal and can hold a conversation, because at the end of the day, they know you’re smart enough to work there they pushed you to the super
Basic but put on a smile / crack a joke if you can, because for these MDs, this is there break from their day and they genuinely enjoy talking to kids who are enthusiastic about Blair

First round interview with vp, basic behaviorals (TMAY, TMAT, etc.), technicals revolved around biotech as this was a life sciences interview (walk me through biotech dcf, how to value biotech, POS, orphan drugs, comparables)