Improving problem solving abilities among students remain to be a challenge among teachers and students. This study aimed to identify problem solving ability of first year students as affected by cognitive development levels and teaching strategies of first year high school students in Mathematics I. The study utilized descriptive and experimental methods. A total of 150 students from three classes in a public secondary school in Central Luzon, Philippines were included. Tools were validated questionnaires to measure problem solving abilities and cognitive development levels. Data were analyzed using frequency, percentage, Mean, Standard Deviation, T-Test, ANOVA, and Regression Analysis. Results showed that the cognitive level of development of the students are satisfactory across all domains (X=2.81). Discovery, Exposition, and Traditional Methods of Teaching were found to significantly improve the problem solving ability of the students with a p-value of 0.000 in each group. All groups have no significant difference in performance which may imply that no teaching method is better than the other. Lastly, cognitive domains of the students in knowledge, comprehension, application and evaluation were found to be significant determinants of students’ problem solving ability. The study results can be a springboard to improve problem solving abilities of high school students. Cognitive development could be considered as a basis for grouping high school students in all curriculum levels and can be evaluated by future researchers for effectiveness.