Internal Auditor applicants have rated the interview process at Vanguard with 2 out of 5 (where 5 is the highest level of difficulty) and assessed their interview experience as 100% positive. To compare, the company-average is 68.4% positive. This is according to Glassdoor user ratings.
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Very easy and straightforward. STAR format type of questions. The position was for an internship but I believe full time interview would have been very similar. Very nice people and there was only one round of interviews.