This research study was conducted to examine the effectiveness of activity-based science teaching practices on the acquisition of problem-solving skills for 5-6 year old preschool children. A total of 32 children were included in this research study. The Personal Information Form and 4-7 Age Problem Solving Ability Scale were used as the data collection tools in the study. Pre-test-post-test control group design was employed. In the experimental group, activity-based science teaching practices prepared by researchers of this study were implemented in 12 weeks (24 integrated activities). In the control group, there was no specific implementation related to problem solving skills other than the Turkish Ministry of National Education Preschool Curriculum. In the analysis of the data, Mann-Whitney U and Wilcoxon Signed-Rank tests were administered. Results showed that activity-based science teaching practices were effective in improving preschool children's problem solving skills.