Lead (Pb) and methylmercury (MeHg) are well-established developmental neurotoxicants, associated with adverse effects on cognition in children. This study estimates the environmental burden of disease associated with Pb and MeHg on IQ loss of children. Human biomonitoring surveys from five European countries were used to estimate exposure for children and women of childbearing age, covering all exposure sources and routes. Coupled with exposure-response functions we derived from meta-analyses, IQ points lost attributable to each metal were estimated. Assuming a normal distribution of IQ points, we calculated the resulting IQ score due to exposure and applied disability weights to calculate DALYs. Uncertainty (on model parameters) and intra-populational variability (exposure differences) were propagated through Monte Carlo simulations. The burden due to combined exposure to both substances was estimated for the French dataset, which met data requirements for a mixture assessment. The estimated IQ shift between exposed and theoretically unexposed individuals was higher for Pb than for MeHg. Pb was responsible for a median shift in IQ points of -0.36 (Sweden) to -0.47 (Czech Republic), while MeHg contributed to -0.03 (Czech Republic) to -0.08 (France) IQ points. We estimated a mean attributable burden from 950 to 1173 DALYs per 100,000 individuals for Pb, and 96 to 251 DALYs per 100,000 for MeHg across the studied countries. The burden of combined exposure in the French population was estimated at an average of -0.49 IQ points lost per individual, and 1,367 DALYs per 100,000 births. Our results highlight the necessity to strengthen regulatory measures to reduce lead exposure through key sources such as dust, tap water, and food, despite decreasing blood levels in Europe in the last few decades. Regarding MeHg, our study highlights the importance of maintaining targeted communication towards current and future parents, especially because dietary exposure remains the main exposure source.