This study examined the effect of employment relations on the work performance of trade unions in Mwanza City Council. It explored the influence of motives for joining trade unions on job expectations, the impact of employee contributions on job responsibilities, and the relationship between trade union benefits and job objectives. Guided by Social Exchange Theory, which emphasizes reciprocity and mutual benefit in relationships, the study investigated how employment relations foster trust and collaboration to enhance employee performance. A quantitative research design was adopted, with data collected from a randomly selected sample of 278 respondents using structured questionnaires. Descriptive and inferential statistics were applied to analyze the data. The findings revealed that motives for joining trade unions accounted for 8% of work performance, while employee contributions explained 7%. Trade union benefits emerged as the strongest predictor, contributing 45.7% to work performance. Overall, employment relations collectively predicted 28.6% of work performance (F = 107.964, p = 0.000) with a standardized coefficient of 0.956. Motives on job expectations (t = 1.700, p = 0.09) and employee contributions (t = 1.235, p = 0.218) did not significantly influence work performance, while trade union benefits showed a significant positive impact (t = 13.420, p = 0.000). The results underscore the importance of employment relations, particularly trade union benefits, in improving work performance. Aligned with Social Exchange Theory, the findings highlight the role of reciprocal relationships in fostering trust, motivation, and productivity. The study recommends that employers strengthen employee-employer relationships by ensuring job security, supporting collective bargaining efforts, and enhancing trade union benefits to foster organizational growth and sustainability.