Customer Complaints Management (CCM) in service firms is imperative to the improvement of marketing performance (MP). Complaint management can also be an important strategy for minimizing dissonance between businesses and clients especially when service quality is taken into consideration. This study therefore explores the mediating role of service quality in the relationship between customer complaint management and marketing performance of selected firms in the service industry, using Nigeria as a case in point. Equity theory provided thought direction for the study based on a survey research design with a quantitative research approach. Copies of a validated questionnaire were shared and a total 218 valid responses were analyzed with the aid of the Jamovi advanced mediation model software to study the relationships between the independent variable-customer complaint management, measured by apology, compensation, and prompt response-and the dependent variable-marketing performance, measured by customer loyalty; with the variables having direct effects, indirect effects and total effects. The total effects show the following the p-value figures, compensation (0.028, 0.008 & 0.001), which means compensation has a significant effect on marketing performance; prompt response (0.363, 0.370, & 0.014), this means that prompt response has just an erratic effect on marketing performance; and apology (0.085, 0.061 & 0.258), which implies that apology has an insignificant effect on marketing performance. Overall, this study concludes that service quality does not have a significant mediating effect in the relationship between CCM and MP. It is recommended, amongst others, that firms in the service sector should regularly monitor and evaluate the effectiveness of complaint management strategies by using customer complaints as feedbacks refine approaches and ensure expectations of customers are met.