As an important environmental pollutant, lead exposure can result in idiopathic developmental intellectual disability (IDII). However, the latest spatiotemporal patterns across the world are unclear. Therefore, in this study, the global burden of lead exposure-related IDII was assessed using the Global Burden of Disease (GBD) study (2019). The data were downloaded from the Institute for Health Metrics and Evaluation (IHME), and the estimated annual percentage change (EAPC) was calculated to assess the changing trend of the age-standardized disability-adjusted life-years (DALYs) rates (ASDR) of global IDII attributed to lead exposure. In 2019, the number of global DALYs of IDII attributed to lead exposure was 2.72 million, the corresponding ASDR was 35.70 per 100,000. The ASDR was highest in children and adolescents, and low- and middle-income countries. From 1990 to 2019, the global number of DALYs of IDII attributable to lead exposure increased by 7.89%, while the ASDR of IDII decreased by 19.19% [EAPC = −0.78, 95% confidence interval (CI): (−0.90, −0.66)]. The downward trends were seen in most GBD regions and countries, especially in high-income countries, but 11 countries presented an upward trend. Therefore, it is important to continue to improve primary mental healthcare globally, especially in low- and middle-income countries. Meanwhile, the implementation of effective strategies to reduce lead exposure should be continually strengthened.