The importance and prominent role of service quality in service industries are inevitable. Previous scholars have investigated relationships among service quality, customer satisfaction, and customer loyalty with fundamental theories in this research era, as proposed in marketing and psychological behavior.  Ergo, their consistencies have been supported by theoretical justification. This research paper aims to determine the effect of service quality on customer loyalty directly and through the mediating role of customer satisfaction and the moderating role of interpersonal relationships in the four-star hotels located in Kuala Lumpur, Malaysia. This research's developed model consists of four latent variables: service quality, customer satisfaction, interpersonal relationship, and customer loyalty. A quantitative approach through the distribution of 550 questionnaires with a response rate of 69.81 percent was taken. Collected data were processed via IBMSPSSAMOS software. Firstly, reliability and factor analysis in order to ensure normality of the collected data, adequacy of sample size were run. Secondly, utilizing structural equation modeling (SEM) via analysis of moment structure (AMOS) program. Confirmatory factor analysis (CFA) with a two-step strategy was run to hypotheses testing. Thirdly, hierarchical regression analyses were conducted for testing the moderating role of interpersonal relationships. Findings supported the notion that service quality has a positive and direct impact on customer satisfaction and loyalty. Customer satisfaction mediates the relationship between service quality and customer loyalty. Finally, interpersonal relationship moderates the relationship between service quality and customer satisfaction positively. Consequently, the interpersonal relationship moderates the relationship between customer satisfaction and customer loyalty positively. This research's originality and value are for academics, practitioners, and managers in service industries, especially hospitality industries and exclusively managers in the four-star hotels in Kuala Lumpur, Malaysia.