The phenomenon of social loafing can be described as a "social disease" due to its negative effects on individuals, social institutions, and organizations in society. This study aimed to examine the validity and reliability of the Turkish version of the Perceived Social Loafing Questionnaire (PSLQ) in the context of young and adult athletes. The participants of the study are composed of young and adult athletes from team sports (football, basketball, volleyball, handball, rugby, and swimming), who were recruited through convenience sampling. The adult participants consisted of 201 athletes (73 female and 128 male; M-age = 21.59 years, SD = 3.84), whereas the young participants consisted of 226 athletes (107 female and 119 male; M-age = 14.43 years, SD = 1.31). The Confirmatory Factor Analysis (CFA) was applied to test the construct validity of the measure, the composite reliability (CR) and average variance extracted (AVE) were calculated to assess the convergence validity, and the correlations with other theoretically-related measures were calculated. Reliability tests included internal consistency coefficient (coefficient alpha), CR, and item-total correlations. The CFA results indicated that the model fits the data well in both participants. Construct validity was also evidenced through correlations with other theoretically-related variables (collective efficacy and perceived social loafing; team cohesion and perceived social loafing) with relationships being negative and significant. Satisfactory convergent validity was achieved through AVE and CR, with values exceeding the acceptable levels of convergence. The reliability coefficients of the measure were suitable for both participants (Cronbach's alpha adult = 0.79; Cronbach's alpha young = 0.77). This study demonstrates that the Turkish version of the PSLQ, which is used to measure the perception of social loafing in teams, has adequate evidence of reliability and validity to support its use in studies with young and adult athletes.