Background: With respect to advancement of the Gestational Diabetes Mellitus (GDM) management plan, the prevalence rate of GDM-related pregnancy complications continues to increase, most likely due to lack of adherence to the recommended GDM management plan. Previous studies have concluded that adherence to the GDM management plan has significantly decreased the incidence of GDM complications. The latest studies on GDM have focused on investigating new interventions to improve pregnancy outcomes; however, evidence about the factors that influence adherence to the recommended GDM management plan is lacking. Purpose: This study aimed to assess the predictors, the barriers, and the motivating factors of adherence to the GDM management plan (i.e. healthy diet, physical activity, self monitoring of blood glucose level, oral hypoglycaemics, and insulin injection) among Arabic-speaking pregnant Omani women with GDM. Methods: A descriptive cross-sectional study was carried out among pregnant women with GDM using a convenience sampling technique, for which 164 participants were recruited from the Antenatal Clinics at Sultan Qaboos University Hospital (SQUH), Royal Hospital (RH), and Khoula Hospital. The measurement scales included a summary of diabetes self-care activities measure (SDSCA), diabetes management self-efficacy scales (DMSES), and social support survey. Multiple-choice questions were used to assess barriers to and motivators of adherence. Multiple linear regression was used to identify predictors of adherence to the GDMmanagement plan among pregnant Omani women with GDM. Descriptive statistics (frequency and percentages) were used to describe the barriers and the motivating factors for adherence. Results: The study included 164 Arabic speaking pregnant Omani women with GDM. Findings from descriptive statistics showed that the study participants have an acceptable level of adherence (M= 6.6 /10) to the GDM management plan, a medium level of self-efficacy (M=121.58/160), and a moderate level of social support (M=78.58/100). In addition, multiple linear regression analysis showed that none of the participants' demographic characteristics (i.e. age, work status, working hours, educational level, income, family history of T2DM, family history of GDM, health education, gravida, para, pre pregnancy weight, pre-pregnancy BMI, social support) is a significant predictor for adherence to the GDM-management plan. However, the stepwise regression revealed three models with three significant predictors, including self-efficacy, previous history of GDM, and the type of GDM management. The major barriers to adherence to the GDM management plan were family, especially kids' responsibilities, time constraints, home responsibilities, and working status. Moreover, participants indicated their concern about maternal and neonatal GDM-related complications and husband encouragement as the main motivating factors for adherence to the recommended GDM-management plan. Conclusion: Understanding among health care providers of the predictors, barriers, and motivators of adherence to the GDM management plan is essential to plan and implement health promotion interventions adapted to the women's personal needs, which will ultimately improve their adherence and pregnancy outcomes. Implications for practice and policy: The study results have implications for both practice and policy. In practice, midwives and antenatal nurses should consider incorporating self-efficacy enhancing strategies and family involvement in their health education interventions to improve adherence to the recommended treatment plan. As for policy, the study suggests collaboration between health policy makers in the Ministry of Health, Consumer Protection Agency, and the Ministry of Municipality to ensure the availability of healthy food choices in the public areas. Further, the Ministry of Manpower should provide flexible working hours and a conducive working environment for pregnant women with GDM to encourage a healthy and active lifestyle.