Few studies have reported the effect of 10-valent pneumococcal conjugate vaccine (PCV10) on otitis media (OM) in infants. In particular, no population-based study in upper-middle income countries is available. In 2010, Brazil introduced PCV10 into its routine National Immunization Program using a 3+1 schedule. We measured the impact of PCV10 on all-cause OM in children. An interrupted time-series analysis was conducted in Goiânia/Brazil considering monthly rates (per 100,000) of all-cause OM outpatient visits in children aged 2-23 months. We used case-based data from the Outpatient Visits Information System of the Unified Health System coded for ICD-10 diagnosis for the period of August/2008 to July/2015. As a comparator, we used rates of outpatient visits due to all-other causes. The relative reduction of all-cause OM and all-other causes of outpatient visits were calculated as the difference between the predicted and observed cumulative rates of the PCV10 post-vaccination period. We then subtracted the relative reduction of all-other causes of outpatient visits from all-cause OM to obtain the impact of PCV10 on OM. In total, 6,401 OM outpatient visits were recorded in 4,793 children aged 2-23 months. Of these, 922 (19.2%) children had more than one OM episode. A significant reduction in all-cause OM visits was observed (50.7%; 95%CI: 42.2-59.2%; p = 0.013), while the reduction in visits due to all-other causes was 7.7% (95% CI 0.8-14.7%; p<0.001). The impact of PCV10 on all-cause OM was thus estimated at 43.0% (95%CI 41.4-44.5). This is the first study to show significant PCV10 impact on OM outpatient visits in infants in a developing country. Our findings corroborate the available evidence from developed countries.