Objective: To assess whether academic achievement among children conceived following fertility treatment is different from that of children born to fertile women while also considering the underlying infertility. Design: Population-based cohort study. Setting: Denmark. Patient(s): The study population consisted of all 154,536 firstborn, live-born, singleton children in Denmark between 1995 and 2000 who completed their ninth grade with an examination. Intervention(s): The Danish Infertility Cohort was used to identify children conceived after fertility treatment (n = 10,099), and information on mean school marks was obtained from Statistics Denmark. Main Outcome Measure(s): Linear regression models were used to estimate mean differences (MDs) and 95% confidence intervals (CIs). Multiple logistic regression models were used to estimate odds ratios (OR) and 95% CI of not passing the ninth-grade examination. Results: The crude overall mean marks for children conceived after the various fertility treatment procedures were in general higher than in children born to fertile women. However, after adjustment for potential confounders, the overall mean marks were statistically significantly lower for children conceived after the various fertility treatment procedures (e.g., any fertility treatment: MD −0.13; 95% CI −0.18, −0.08) compared with children born to fertile women. Further, children conceived after any fertility treatment had a statistically significant lower crude likelihood of not passing the ninth-grade examination (OR 0.66; 95% CI 0.53, 0.81) compared with children born to fertile women, whereas no difference was observed in the confounder adjusted analyses (OR 1.15; 95% CI 0.89, 1.49). When children born to women requiring fertility assistance but without fertility treatment in the index pregnancy were used as a reference group, no differences in the adjusted overall mean marks and the likelihood of not passing the ninth grade with an examination were observed. Conclusion: Our findings indicate that fertility treatment per se is not associated with lower school marks and the likelihood of not passing the ninth grade with an examination. Hence, we suggest that factors related to both fertility problems and cognitive development may more likely explain the slightly lower academic performance (i.e., modest lower mean marks) among children conceived after fertility treatment.