Young children have better math abilities when their parents engage in more math-related conversations with them. Yet, previous studies have found that math talk occurs only very infrequently in everyday interactions. In the present study, we sought to promote adult-child conversations about math in a naturalistic context using minimal instructions. We observed 179 adult-child dyads while they shopped in grocery stores with signs prompting them to engage in math-related conversations (math condition), signs prompting them to talk about other topics (general language condition), or without any signs (baseline condition). In the math condition, more adults talked about math compared to the general language or the baseline condition, and this finding could not be explained by demographic characteristics of the dyad or the overall amount of conversations. This study demonstrates that cost-effective signs placed in everyday contexts can promote math-related conversations and potentially provide math learning opportunities for children.