The relationship between distinct dietary selenium intake and type 2 diabetes (T2D) is still a topic of uncertainty. This study examined the relationship between dietary selenium intake and T2D risk among middle-aged and older Chinese adults. Dietary selenium intake was assessed through three 24 h recalls, using data from the China Health and Nutrition Survey. To investigate the relationship and the potential dose–response pattern between selenium intake and the likelihood of developing T2D, we employed both the restricted cubic spline analysis and the Cox proportional hazards model as our analytical tools. A cohort of 5970 participants aged ≥ 50 years was followed for an average of 5.44 years. The results revealed a V-shaped correlation between selenium intake and T2D risk, with the lowest risk observed at approximately 45 µg/day. Below this level, the risk decreased with an increasing selenium intake, while the risk increased between 45 and 100 µg/day. No significant association was found beyond 100 µg/day. These findings suggest that both low and high selenium consumption may increase T2D risk, highlighting the importance of maintaining a balanced selenium intake for T2D prevention.