Spatial thinking, an important component of cognition, supports academic achievement and daily activities (e.g., learning science and math; using maps). Better spatial skills are correlated with more spatial play and more parental attention to spatial concepts. Tested here was whether informing mothers about spatial thinking and ways to encourage it would increase the spatial guidance they provide to their preschool children (N = 41; M = 5.23 years) during dyadic block play. Mothers given such instructions indeed produced more spatial language and spatial guidance than mothers asked to play as usual. In instructed dyads, children also used more spatial language; both mothers and children engaged in less pretend play. Findings offer support for designing interventions to encourage parents to foster their children's spatial skills.