Understanding personality characteristics that help and/or hinder competitive success in sport is of great interest to many sport psychology researchers. Two such personality characteristics that have been linked to the achievement-striving process in competitive sport are grit and perfectionism. While grit—as conceptualized by Duckworth, Peterson, Matthews, and Kelly (2007)—is largely associated with adaptive characteristics and outcomes in sport, perfectionism has been labeled as a 'dual effect' characteristic (MacNamara & Collins, 2015) that has been linked to both adaptive and maladaptive outcomes/processes in sport. The purpose of this study was to examine previously unexplored relationships between facets of multidimensional grit and multidimensional perfectionism in sport. A sample of 251 intercollegiate student-athletes (M age = 20.34 years, SD = 2.0) completed measures of domain-specific grit and domain-specific perfectionism in sport. Hierarchical regression analyses revealed that (a) separate facets of perfectionistic concerns negatively predicted grit, and (b) separate facets of perfectionistic strivings positively predicted grit in sport. Canonical correlation analysis produced an adaptive profile of perfectionism (i.e., a canonical variate comprising low perfectionistic concerns and high perfectionistic strivings) that was positively correlated (RC = .61, p < .001) with a grit variate comprising moderate consistency of interests and high perseverance of effort. The results not only reinforce the importance of conceptualizing/measuring grit and perfectionism as multidimensional constructs, but also indicate that the combination of high grit, low perfectionistic concerns, and high perfectionistic strivings may form part of a 'positive personality profile' that might assist athletes in the achievement-striving process in sport.