Background: Maternal fish consumption during pregnancy has been positively associated with cognitive and visual abilities in the offspring, leading to the hypothesis that maternal omega-3 (n23) long-chain PUFA (LCPUFA) supplementation improves children's neurologic and visual development. Objective: The objective was to evaluate the effect of maternal omega-3 LCPUFA supplementation in pregnancy on neurologic and visual development in the offspring. Design: Five electronic databases were searched. Human randomized controlled trials that supplemented the maternal diet with omega-3 LCPUFAs during pregnancy, or pregnancy and lactation, and that assessed either neurologic or visual development of the offspring were included. Trial quality was assessed, and the results of eligible trials were compared in meta-analyses. Results: Eleven RCTs involving 5272 participants were included in the review. Most trials had methodologic limitations. No differences in standardized psychometric test scores for cognitive, language, or motor development were observed between the LCPUFA-supplemented and control groups, except for cognitive scores in 2-5-y-old children, in whom supplementation resulted in higher Developmental Standard Scores (mean difference: 3.92; 95% CI: 0.77, 7.08; n = 156; P = 0.01). However, this effect was from 2 trials with a high risk of bias. Because of the variety of visual assessments and age ranges, it was not possible to combine studies with visual outcomes in a meta-analysis, although 6 of the 8 assessments in 5 trials reported no difference between the supplemented and control groups. Conclusion: The evidence does not conclusively support or refute that omega-3 LCPUFA supplementation in pregnancy improves cognitive or visual development.