Diabetes is a metabolic disorder that can affect nearly all organ systems in the body. Recently, Vitamin D3 was given some importance worldwide in the pathogenesis of diabetes. Deficiency in vitamin D3 appears to be linked to the development of type II diabetes and metabolic syndrome. To estimate the serum levels of Vitamin D and HbA1c among obese type II diabetic patients., and to find out the relationship between BMI with serum levels of Vitamin D and HbA1c among study participants. A cross-sectional study design for a period extended from 25th December 2021 to 10th February 2022, a total of 40 obese type II diabetes patients was selected from Al-Wafa Medical Center by non-probability sampling at Mosul city in Northern Iraq. The estimation of vitamin D and HbA1c was done by using CL900i and BS230Mindray. Statistical Package for Social Sciences (SPSS) version 26 was used for statistical data analysis. Obese type II diabetes patients exhibited a highly significant decrease (at P-value < 0.001) in the serum level of vitamin D (t = 17.852) with a mean (12.2180 ± 4.32852). A positive correlation (r =0.899) between HbA1c level and BMI, and an inverse correlation (r = -0.867) between vitamin D and body mass index (BMI) at P-value < 0.001. Low vitamin D levels and elevated HbA1c are common in obese type II diabetic patients. A positive correlation between HbA1C and body mass index (BMI) and vitamin D inversely correlate with body mass index (BMI).