The present study was designed to examine differences in the effect of the number of children in the household (also known as “parity”) on the relationship between initiating joint attention (IJA) and language development. We reasoned that infants who are only children (i.e., in uniparous homes), relative to infants who have one or more siblings (i.e., in multiparous homes), would have more opportunity to engage in IJA, and would, therefore, acquire a larger number of object labels. We tested the hypotheses that: 1) there would be a positive correlation between the number of IJA bids and language overall, and 2) parity would moderate the IJA-language relationship such that in uniparous households, the aforementioned correlation would be stronger than in multiparous homes. Joint attention was measured using the Early Social Communication Scales (ESCS) Picture Book Task, and language was assessed through parental report on the MacArthur-Bates Communicative Development Inventory (MBCDI). There was no significant correlation between IJA and language on the whole, though there was a significant correlation for infants in uniparous homes between IJA and language. This finding partially supports Hypothesis 2 in terms of the IJA-language relationship being stronger in uniparous homes rather than multiparous ones, though it was only true for productive vocabulary. These null findings may provide reassurance for families with multiple children that their younger children are not at an IJA/language acquisition disadvantage.