Background: Infertility affects about 15% of all couples worldwide. Male factors such as decreased semen quality contribute to around 40% of the cases. Recent reviews have shown that different foods and nutrients may improve semen quality. Objectives: We conducted a systematic review in order to investigate whether intake of omega-3 fatty acids can improve semen quality markers. Materials and methods: A systematic search of PubMed, Embase, and Cochrane was conducted in adherence with the PRISMA guideline from the earliest available online indexing year to October 2018. Keywords related to male fertility or infertility was combined with words describing omega-3 fatty acids and dietary fish intake. RCTs and observational studies on infertile and fertile men were included. Studies were considered eligible if they met the inclusion criteria, evaluated either the effect of omega-3 fatty acids or dietary fish intake and had semen quality as primary outcome. Results: Thousand and seventy four records were screened, and sixteen studies were ultimately included. Fourteen of the included studies found an improvement or association between omega-3 and at least one semen quality marker. As the studies were very inhomogeneous in participants (fertile/infertile, age, BMI, ethnicity etc), no meta-analysis was performed. Discussion: The findings in this review are limited by the few available RCTs. Furthermore, RCTs were very heterogenetic according to study population, sample size, dosage of omega-3, and durations of follow up. Results from the observational studies might have been affected by recall bias and confounded by lifestyle factors. Conclusion: Based on the findings in this review, omega-3 supplements and dietary intake of omega-3 might improve semen quality parameters in infertile men and men from couples seeking fertility treatment. However, more research is required in order to fully clarify the effect of omega-3 on semen quality and research with fecundity as end point is needed.