Background: Quality of life (QoL) is the most important indicator for assessing the status of health care in chronic diseases. The present study aimed to determine the pathway determinants model of QoL in patients with gestational diabetes mellitus (GDM). Methods: This cross-sectional study was conducted on 329 women with GM referred to health care centers in Qom, Iran during 2018. Convenience sampling methods was used. Inclusion criteria were: afflicted by GM and received pregnancy care services from health center. Several questionnaires (Knowledge, attitude, self-efficacy (SE), social support (SS), pregnancy distress, self-management(SM) and QoL) were used for data collection. Data were analyzed with SPSS-21 and Lisrel-8.8 software using statistical path analysis. Results: The mean age of participants was 30.93 ± 5.42 years. The final path model fitted well (CFI =1, RMSEA = 0.0003) and showed that, only age variable from both direct and indirect path had an impact on QoL (B = 0.51). Among variables that directly affected the QoL, SS had the highest effect (B = 1.02) and SE (B = 0.01) had the lowest effect. In the indirect path, only the knowledge variable by affecting the SE had an impact on the QoL (B = 0.0045). Conclusion: SS had the greatest impact on the QoL. Obviously, providing all the requirements to support patients can help them overcome problems and improve their QoL. Distress negatively affects the QoL through SM and it should be noticed in interventional studies.