Late talkers are children with fewer than 50 words and no two-word combinations by age 2. While some late talkers catch up with typically developing peers, others remain susceptible to developmental language disorders and language-related academic challenges throughout school years. Although maternal input plays a crucial role in language development, its impact on late talkers remains underexplored. This study examines how maternal input quality affects late talkers' lexical diversity and productive syntax, utilizing conversational data from Ellis Weismer's (2007) corpus in CHILDES (MacWhinney, 2000). We analyzed 76 mother-child samples from 38 late talkers (ages 2;6–3;6) in CLAN, assessing lexical diversity with lexical D, productive syntax with IPSyn, and maternal input quality with MLU, lexical D, and IPSyn. Linear regression models indicate that maternal input quality contributes to late talkers’ syntactic development but negatively affects their lexical diversity. These findings underscore the complex nature of maternal input in late talkers’ language development.