This study aimed to examine the influence of internal service quality (ISQ) on job performance in the public sector. Data was collected from 250 police personnels in PDRM in Kuching using survey method with questionnaire as the main tool. The instrument used to measure internal service quality was assessed via Kang et al.’s (2002) 22-item uni-dimensional measure of internal service quality battery (ISQB). Job performance was measured using an instrument developed by Borman & Motowidlo (1993). Results of the instrument's Cronbach Alpha measurement showed that the score of reliability is above 0.70 which indicates an acceptable level. The results indicate that internal service quality is positively correlated with job performance. This study provides insights on the relationship between internal service quality and job performance in the public sector. The findings of this study may help the public sector to enhance its internal service quality and its effect on job performance. Limitations and recommendations are also discussed.