Links between the development of early literacy and math skills are well documented. This systematic review focuses on how literacy is incorporated into informal math intervention studies for children in preschool to third grade, which has implications for researchers and those training caregivers to support their children at home. We reviewed 51 experimental or quasi-experimental studies published from 1981 to 2021 that investigated the effectiveness of math interventions in informal learning environments with a caregiver interventionist. Findings revealed that 100% of studies included literacy in some way. We also investigated what types of literacy activities were integrated, how literacy was a part of data sources collected, and in what ways literacy was mentioned explicitly by authors in research reports. The most common literacy activity was speaking and listening, and the most frequently included literacy data source was standardized literacy achievement measures. Finally, researchers in the included studies did not detail literacy throughout their research reports. While early math interventions often integrate literacy, the research base including math interventions would benefit from more explicit rationales for their use of literacy, and caregivers should be provided information to help understand how literacy should be a part of the way they work with their child on math at home.