Research literature suggested that participative decisions of professionals in nonprofit associations could be affected by such motivational factors as rational choice, affective bonding, and normative conformity of individuals (Knoke, 1988). However, there is a dearth of studies conducted on the membership incentives of athletics-related professional associations. Why do athletic administrators and coaches spend their time and pay membership dues to engage in the activities of associations? What are the detailed motives affecting decisions of members to enroll in their respective organizations? The study was designed to explore the essential incentives of associational enrollment, develop a valid and reliable instrument to measure membership motives, and confirm a conceptual model to provide fruitful references for the organizers of athletics-related professional associations. Through the phases of content validation, data collection, and construct validity, a 4-factor model derived from theoretical framework was constructed and a 20-item Scale of Membership Incentives (SMI) was tested. The voluntary participants (N=427) included an expert panel (n=12) in the phase of content validation, and nationally sampled 415 athletic administrators (n=168) and head coaches (n=247) who were active members of their respective associations in the phase of construct validity. The data was randomly split into two-halves as calibration (A) and validation (B) samples, and undertaken by multiple statistical analyses. Sample A was examined by Exploratory Factor analysis (EFA) using Principle Components Analysis of SPSS 10.0 to explore the structure of interrelationships among items. Sample B was analyzed in Confirmatory Factor analysis (CFA) utilizing LISREL 8.50 to validate the constructs of SMI and confirm the model. The entire sample was further tested with CFA for ensuring sampling accuracy (Bentler, 1990). EFA extracted four significant (Utilitarian, Purposive, Solidary, and Informative) incentive factors containing14 retained items with factor loadings higher than .40. CFA findings of Sample B (X2/df=3.25, RMSR=.048, GFI=.96, IFI=.94, CFI=.94) indicated the 4-factor model fitting well the data and this was also ensured by CFA confirmation of entire sample. Alpha reliabilities (.704 - .733), composite coefficients (.830 -.854), and variance-extracted measures (.57 - .66) provided satisfactory statistical evidences supporting the internal consistency and construct validity of SMI factors. The study enriched referential inventory for utility of associational organizers to assess membership incentives in athletics-related professional associations, and assisted enhancement of comprehension about importance of diverse inducements for continuous growth of the nonprofit associations.