Developing critical thinking skills in adults empowers them to make sound decisions. Seventy-one parents in a low-income preschool program took part in a study to develop their critical thinking skills. A two-group (experimental, control) randomized, pretest-posttest design was used. The experimental group participated in two 45-minute sessions about vegetables and physical activity. The development of a methodology to assess critical thinking included a context-specific definition, problem solving, and the use of scenarios. After the intervention, parents in the experimental group showed improvement in problem solving, especially in areas of problem identification, gathering relevant information to solve the problem, and providing solutions to the problem. Little change was seen in areas of providing rationale and judging the soundness of decisions. Interventions of longer duration could lead to a change in these higher levels of critical thinking. The development of critical thinking skills seems plausible in informal educational settings with low-income audiences.