This study evaluate the association of 25 (OH)D levels in pregnancy with GDM as a case group (n=31) and without GDM as a control group (n=31), and the association between levels of 25 (OH)D in pregnancy with OGCT 50g and OGTT 100g fasting, 1 hour, 2 hours, and 3 hours. This study is an unmatching hospital-based case-control at Dr. Soetomo and Airlangga University hospital Surabaya from February 2022 to May 2022, GDM was diagnosed according to the ADA guidelines. Vitamin D status was defined as, levels of 25 (OH)D normal (30-100 ng/mL), insufficiency (20-29.9 ng/mL), deficiency (<20 ng/mL). The mean serum 25(OH)D level was lower in case group 14.7 + 4.09 ng/mL compared to that in control group 28.9 + 9.10 ng/mL. There was a significant association between 25(OH)D levels and GDM (p=0.001). Samples with deficiency 25(OH)D 11.94 times that increases the risk of developing GDM. There was a significant association between 25(OH)D levels and OGCT 50g levels (p=0.001). There was no significant association between 25(OH)D levels with OGTT levels of 100g fasting (p=0.747), 1 hour (p=0.148), 2 hours (p=1,000), and 3 hours (p=0.469).