In this research the effects of STEM applications, which are aimed to support the integrated teaching knowledge of pre-service science teachers on the problem solving skills of pre-service science teachers were examined. The research was carried out in scope of the mixed method design of convergent parallel design. The research was conducted with pre-service science teachers of experimental group (n=31) and control group (n=31) who were studying at Firat University. STEM applications including Algodoo were carried out with the pre-service teachers in the experimental group for one term. The data of the research were collected through the problem solving inventory test (PSIT), prospects diaries during the process of the pre-service science teachers in the experiment group. Quantitative data were analyzed using unpaired samples t-test. Statistically significant differences were found in favor of the experimental group when the PSIT post-test scores of the pre-service teachers in the experimental and control groups were analyzed. They said that STEM education is necessary and important for them, much better products arise as a result of gathering different disciplines, but integration of four disciplines is not easy.