Objective: To obtain internal and external validity evidence supporting the use of the Sport Multidimensional Perfectionism Scale (Sport-MPS: Dunn, J. G. H., Causgrove Dunn, J., & Syrotuik, D. G. (2002). Relationship between multidimensional perfectionism and goal orientations in sport. Journal of Sport & Exercise Psychology, 24, 376-395) as a measure of perfectionist tendencies in sport. Internal validity evidence was gathered by examining the factorial composition and factor structure of the Sport-MPS. External validity evidence was gathered by examining the relationship between the subscales of the Sport-MPS and the subscales of an established measure of global perfectionism. Method: Independent samples of male Canadian Football players (n = 276, M age = 18.29 years), male youth ice hockey players (n = 229, M age = 14.15 years), male and female intercollegiate team-sport athletes (n = 22 1, M age= 21.45 years), and female figure skaters (n = 12 1, M age= 14.46 years) completed the Sport-MPS. A sub-sample of football players (n = 138) and all figure skaters also completed the Multidimensional Perfectionism Scale (Hewitt-MPS: Hewitt, P. L., & Flett, G. L. (1991). Perfectionism in the self and social contexts: Conceptualization, assessment, and association with psychopathology. Journal of Personality and Social Psychology, 60, 456-470) which served as a criterion measure of perfectionism. Results: Confirmatory factor analyses failed to support the factor structure of the Sport-MPS suggested by Dunn et al. However, follow-up exploratory factor analyses suggest the Sport-MPS is comprised of four latent dimensions that measure personal standards, concern over mistakes, perceived parental pressure, and perceived coach pressure. Each factor was highly interpretable and corresponded to the factors proposed by Dunn et al. Statistically significant bivariate correlations, standardized regression coefficients, and canonical correlations (all ps < 0.05) revealed that the subscales of the Sport-MPS were related to the subscales of the Hewitt-MPS. Conclusions: The internal structure of the Sport-MPS was quite robust across heterogeneous samples of competitive athletes. The anticipated relationships between Sport-MPS and Hewitt-MPS subscales support the use of the Sport-MPS as a measure of interpersonal and intrapersonal dimensions of perfectionism in sport. Further construct validation of the Sport-MPS is recommended. (c) 2005 Elsevier Ltd. All rights reserved.