We examined the language input of parents of infants at high and low familial risk for autism spectrum disorder (ASD) and investigated reciprocal associations between parent input and child language skills in the first 2 years of life. Parent‐infant dyads (high‐risk: n = 53; low‐risk: n = 33), 19 of whom included an infant later diagnosed with ASD, were videotaped during free play interactions at 12, 18, and 24 months. Measures of parent input were derived from parent–child interactions. Children's language skills were assessed using the Mullen Scales of Early Learning at 12, 18, and 24 months. Results suggested that (a) parents of high‐ and low‐risk infants produced similar word tokens, word types, and proportions of contingent verbal responses, but parents of high‐risk infants used shorter mean length of utterances (MLU) than parents of low‐risk infants at 18 and 24 months; (b) parents' MLU at 18 months was positively associated with their infants' language at the subsequent visit after 6 months, regardless of group; and (c) infants' language at 18 months was positively associated with parents' MLU at the subsequent visit after 6 months in the high‐risk group only. These findings contribute to our understanding of the mechanisms underlying early language learning of high‐risk infants who have an increased risk for language delays and deficits.