The phenomenon of first impression is well researched in social psychology, but less so in the study of OSCEs and the multiple mini interview (MMI). To explore its bearing on the MMI method we included a rating of first impression in the MMI for student selection executed 2012 at the University Medical Center Hamburg-Eppendorf, Germany (196 applicants, 26 pairs of raters) and analyzed how it was related to MMI performance ratings made by (a) the same rater, and (b) a different rater. First impression was assessed immediately after an applicant entered the test room. Each MMI-task took 5 min and was rated subsequently. Internal consistency was α = .71 for first impression and α = .69 for MMI performance. First impression and MMI performance correlated by r = .49. Both measures weakly predicted performance in two OSCEs for communication skills, assessed 18 months later. MMI performance did not increment prediction above the contribution of first impression and vice versa. Prediction was independent of whether or not the rater who rated first impression also rated MMI performance. The correlation between first impression and MMI-performance is in line with the results of corresponding social psychological studies, showing that judgements based on minimal information moderately predict behavioral measures. It is also in accordance with the notion that raters often blend their specific assessment task outlined in MMI-instructions with the self-imposed question of whether a candidate would fit the role of a medical doctor.