The present study examined parental guidance of young children's inquiry during joint interactions in the home environment. Half of the parents received inquiry-based guidance instructions, encouraging their children to observe, question, predict, and evaluate; the control group received no information about guidance. Thirty-two families were observed in their homes, conducting an initial paw print matching activity and a seed sorting activity one month later. The results indicated that although all parents provided significant support for science and mathematics, parents who received inquiry guidance instructions facilitated children's complex reasoning through support of advanced inquiry processes such as comparing, predicting, and evaluating. The findings provide evidence that parents can be encouraged to support young children's inquiry learning through simple methods of instruction and highlight the need for coordination between early childhood educational and home contexts to support preschoolers' learning.