Aims: To assess vitamin D status among Gestational Diabetes Mellitus pregnant women in Gaza Strip. Study Design: Case control study. Place and Duration of Study: Samples were collected from pregnant women attending primary health care centers, Gaza, Gaza Strip. Methodology: The study comprised 90 participants, 45 GDM pregnant women and 45 apparently healthy pregnant women. Serum vitamin D and insulin levels were measured by ELISA, fasting blood glucose (FBG), 2 h oral glucose tolerance test (OGTT), glycated hemoglobin (HbA1c), triglycerides (TG), cholesterol, high-density lipoprotein (HDL), phosphorus and calcium were determined chemically. Blood pressure was measured. Body mass index (BMI) and low-density lipoprotein (LDL) were calculated. Ethical approval was acquired from Helsinki committee. All data was analyzed using the SPSS program. Results: The average vitamin D in GDM cases was lower than that in controls (P=0.031). There was an increase in the average of FBG, OGTT, HbA1c and insulin levels in GDM cases versus controls (P<0.001). The average levels of serum cholesterol, TG and LDL were significantly higher in cases as compared to controls. The average systolic and diastolic blood pressure levels were higher in GDM cases in relation to controls. Pearson correlation test showed a significant negative correlation between vitamin D and the parameters: BMI, glucose, OGTT, HbA1c and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). Conclusion: Vitamin D was lower in GDM women compared to controls. Low vitamin D status may be associated with insulin resistance and act as a risk factor for GDM.