Despite extensive research on the importance of soft skills development and mentoring in cooperative education, no identifiable study provides a method to assess mentorship effectively, especially in engineering cooperative education. This study examines which mentoring function—psychosocial or career—would better help students improve soft skills during their cooperative education program. Methodologically, this study utilizes a longitudinal survey distributed both before and after the cooperative education program. From Summer 2014 through Fall 2014, eight universities with engineering cooperative education programs agreed to participate in the study with a total of 11 cooperative education cycles (three universities participated both in summer and fall cycles). Study participants are engineering students as they participate in their cooperative education programs. The study includes a survey developed based on Noe’s mentoring function scale (Noe, 1988) and Kantrowitz’s Soft Skills Performance Measurement (SSPM) (Kantrowitz, 2005). Results indicate that psychosocial mentoring is a better mentoring function to help engineering students in developing their soft skills during a cooperative education program.