Abstract

Purpose: This study examines how relationship quality moderates the relationship between service quality dimensions and customer loyalty in third-party logistics (3PL) services for small and medium enterprises (SMEs). Research design, data and methodology: A quantitative approach was employed using survey data from 308 SMEs in Thailand utilizing 3PL services. The SERVQUAL framework measured service quality across five dimensions: tangibles, reliability, responsiveness, assurance, and empathy. Relationship quality and customer loyalty were assessed using validated multi-item scales. Partial Least Squares Structural Equation Modeling (PLS-SEM) analyzed the direct and moderating effects. Results: Four service quality dimensions significantly influenced customer loyalty: reliability, responsiveness, assurance, and empathy, with empathy showing the strongest effect. Tangibles did not significantly impact loyalty. Critically, relationship quality significantly moderated the effects of reliability, responsiveness, assurance, and empathy on loyalty, demonstrating that strong relationships amplify service quality benefits. The model explained 65% of variance in customer loyalty. Conclusions: Service quality alone is insufficient for building loyalty in SME-3PL partnerships. Providers must integrate service excellence with relationship development strategies. The findings advance theoretical understanding of service quality-loyalty mechanisms in B2B logistics contexts and provide actionable insights for 3PL providers serving resource-constrained SMEs.