Objectives: Burnout is a work-related syndrome with growing relevance in occupational health. This study explored the association between job stress factors and burnout in Korean workers at small- and medium-sized enterprises (SMEs). Material and Methods: A total of 1024 employees from SMEs (50–299 workers) receiving outsourced occupational health services completed a cross-sectional survey. Job stress was measured using the Korean Occupational Stress Scale short form (KOSS), and burnout was assessed with the Korean version Burnout Syndrome Scale (KBOSS), aligned with International Classification of Diseases, 11th Revision (ICD-11) criteria. Burnout was evaluated across 3 dimensions: exhaustion, cynicism, and reduced efficacy. Burnout syndrome was defined as meeting all 3 dimensions. Multiple logistic regression analyses were performed to assess the associations between job stress factors and burnout. Results: Burnout syndrome was found in 3.3% of participants. Key findings with statistical measures include: 1) burnout syndrome association – high job demand (Q3: OR = 12.62, 95% CI: 2.03–78.41, p < 0.05) and high overall job stress (Q4: OR = 17.56, 95% CI: 1.40–220.76, p < 0.05); 2) exhaustion predictors – high job demand (Q3: OR = 10.71, 95% CI: 3.64–31.48, p < 0.001), inadequate compensation (Q4: OR = 2.06, 95% CI: 1.02–4.16, p < 0.05), and poor workplace culture (Q4: OR = 2.63, 95% CI: 1.11–6.24, p < 0.05); 3) paradoxical findings – low job autonomy associated with reduced exhaustion (Q4: OR = 0.23, 95% CI: 0.11–0.48, p < 0.001). Conclusions: Specific job stressors differentially impact burnout dimensions in Korean SMEs: Job demand and overall stress critically predict burnout syndrome, while inadequate compensation and poor workplace culture significantly affect exhaustion. The counterintuitive protective effects of reduced autonomy warrant further investigation. Organizations should prioritize evidence-based workload management and compensation fairness aligned with ICD-11 diagnostic patterns. Int J Occup Med Environ Health. 2025;38(5)