This study was aimed to determine the relationship of physical activity (PA) with the neighborhood environment and social support for PA among patients with diabetes mellitus (DM).<b> </b>A total of 193 consenting individuals with DM attending endocrinology clinic in a Nigerian tertiary hospital participated in this cross-sectional study. The<b> </b>international physical activity questionnaire short form, physical activity neighborhood environment scale (PANES), and physical activity and social support scale (PASSS) were used to assess the PA level (low, moderate, and high), neighborhood environment and social support for PA, respectively. The results of bivariate analyses showed that all elements of built environment and social support were significantly associated with PA. Regression model analyses indicate that PANES score was associated with moderate (adjusted odds ratio [aOR]: 10.76; 95% confidence interval [CI]: 3.82-30.32) to high (aOR: 45.73; 95% CI: 12.14-172.27) PA. In addition, easy access to quality walking facilities (aOR: 46.53; 95% CI: 3.89-557.32; aOR: 46.13; 95% CI: 2.65-802.40) and easy access to recreation infrastructure (aOR: 46.89; 95% CI: 3.95-487.83; aOR: 17.99; 95% CI: 1.28-252.98) were associated with moderate to high PA, respectively, while safety from crime (aOR: 0.21; 95% CI: 0.07-0.64) and easy access to services and shops (aOR: 21.90; 95% CI: 1.83-262.59) were associated with moderate and high PA. Informational social support was associated with moderate PA (aOR: 1.44; 95% CI: 1.04-2.00). In conclusion, the neighborhood environmental and social support factors were associated with the PA activity level among Nigerian patients with DM.