Background: The quality of healthcare services is one of the important factors in determining patient satisfaction. In outpatient services for BPJS referral patients, several problems such as waiting time, information delivery, and facility comfort may affect patients’ assessment of hospital services. Objective: This study aimed to determine the relationship between healthcare service quality and patient satisfaction among BPJS referral outpatients at Sultan Agung Islamic Hospital Semarang. Methods: This study used an analytical observational design with a cross-sectional approach involving 96 BPJS referral outpatients. Samples were selected using consecutive sampling. Healthcare service quality was measured based on five dimensions, namely tangible, reliability, responsiveness, assurance, and empathy, while patient satisfaction was assessed based on expectation conformity, intention to revisit, and willingness to recommend the service. The relationship between variables was analyzed using the Spearman correlation test. Results and Discussion: A total of 49 respondents (50.5%) rated the quality of healthcare services as adequate, while 48 respondents (49.5%) rated it as good. Most respondents were moderately satisfied, accounting for 58 respondents (59.8%), while 39 respondents (40.2%) were satisfied. The Spearman correlation test showed a coefficient of r = 0.786 with p < 0.001, indicating a significant, positive, and strong relationship between healthcare service quality and patient satisfaction. Better perceived service quality was associated with higher patient satisfaction. Conclusion and Recommendation: There was a positive and strong relationship between healthcare service quality and patient satisfaction among BPJS referral outpatients at Sultan Agung Islamic Hospital Semarang. The hospital is recommended to continuously improve service quality, particularly service timeliness, staff communication, and the comfort of facilities and infrastructure, to increase patient satisfaction.