IMPORTANCE Hearing loss (HL) in children can be deleterious to their speech and language development. The standard of practice has been early provision of hearing aids (HAs) to moderate these effects; however, there have been few empirical studies evaluating the effectiveness of this practice on speech and language development among children with mild-to-severe HL. OBJECTIVE To investigate the contributions of aided hearing and duration of HA use to speech and language outcomes in children with mild-to-severe HL. DESIGN, SETTING, AND PARTICIPANTS An observational cross-sectional design was used to examine the association of aided hearing levels and length of HA use with levels of speech and language outcomes. One hundred eighty 3- and 5-year-old children with HL were recruited through records of Universal Newborn Hearing Screening and referrals from clinical service providers in the general community in 6 US states. INTERVENTIONS All but 4 children had been fitted with HAs, and measures of aided hearing and the duration of HA use were obtained. MAIN OUTCOMES AND MEASURES Standardized measures of speech and language ability were obtained. RESULTS Measures of the gain in hearing ability for speech provided by the HA were significantly correlated with levels of speech (ρ179 = 0.20; P = .008) and language: ρ155 = 0.21; P = .01) ability. These correlations were indicative of modest levels of association between aided hearing and speech and language outcomes. These benefits were found for children with mild and moderate-to-severe HL. In addition, the amount of benefit from aided hearing interacted with the duration of HA experience (Speech: F4,161 = 4.98; P < .001; Language: F4,138 = 2.91; P < .02). Longer duration of HA experience was most beneficial for children who had the best aided hearing. CONCLUSIONS AND RELEVANCE The degree of improved hearing provided by HAs was associated with better speech and language development in children. In addition, the duration of HA experience interacted with the aided hearing to influence outcomes. These results provide support for the provision of well-fitted HAs to children with HL. In particular, the findings support early HA fitting and HA provision to children with mild HL.