The main purpose of this study is to investigate the effects of problem solving approaches on pre-service elementary teachers' basic mathematics achievement and problem-solving performance. The study has been conducted as quasi - experimental design with 110 elementary school pre-service teachers at a public University in Central Anatolia Region. The study has lasted 12 weeks. Experimental group has been instructed by questioning problem solving approach while control group has been instructed by traditional problem solving approach. The data have been collected through Basic Mathematics Achievement Test, Mathematical Problem Solving Test and has been analyzed by using multivariate analysis of covariance. The results have revealed that questioning problem solving approach has a statistically significant effect on pre-service elementary school teachers' basic mathematics achievement and problem solving performance (The effect size has been found as eta(2) = 0.265).