Background: Safety data on disease-modifying therapies (DMTs) for relapsing multiple sclerosis (RMS) during breastfeeding are limited. Objective: Assess safety outcomes for offspring breastfed by mothers undergoing glatiramer acetate (GA; Copaxone^®) treatment. Methods: This non-interventional, retrospective study used German Multiple Sclerosis and Pregnancy Registry data. Participants had RMS, a live birth, and received GA or no DMT during breastfeeding. Results: GA cohort: 58 mothers/60 offspring; matched controls: 60 mothers/60 offspring; 86.7% (GA) and 25% (control) of offspring were born to mothers who had GA at some point during pregnancy. Maternal demographics and disease activity were comparable. Annualized number of hospitalizations was similar for breastfed offspring: 0.20 (95% confidence interval: 0.09–0.31; GA) and 0.25 (0.12–0.38, controls). Proportion of offspring requiring hospitalization was comparable between cohorts (18.33% vs. 20.00%). Annualized number of antibiotic uses was similar in both cohorts (0.22, 0.10–0.33 (GA) vs. 0.17, 0.06–0.27 (controls)) The proportion of offspring requiring antibiotics was 15.00% (both cohorts). More developmental delays were identified in controls versus the GA cohort (3 (5.36%) vs. 0). Growth parameters were comparable between cohorts. Conclusion: Maternal intake of GA during breastfeeding did not adversely affect offspring safety outcomes assessed during the first 18 months of life.