This study focuses on determining the significant effect on teacher’s utilization of Thematic Approach on the learner’s critical thinking abilities and problem-solving skills. It seeks to determine the level of Thematic approach, learners’ critical thinking abilities and problem-solving skills. The significant difference in the learners’ problem-solving skills before and after using the Thematic Approach. The significant effect on teacher’s utilization of thematic approach on the learner’s critical thinking abilities, and significant effect on the learner’s problem-solving skills before and after the teacher’s utilization of Thematic Approach. The study used Quasi-Experimental research design. The research was conducted among the Grade 11 students of Majada In Integrated School during the school year 2023-2024. A purposeful sampling strategy is used to determine the respondents in the study. The research instrument used is the researcher-made survey questionnaire checklist which is prepared, checked, and submitted to reputable experts in the field of the study. A teacher made test is utilized to determine the before and after scores of the respondents and a questionnaire checklist to describe the level of thematic approach and critical thinking abilities. Most of the learners strongly agree with very highly evident as interpretation of the utilization of the Thematic approach as to integrative, cross curriculum, world relevance and engagement. The level of learners’ critical thinking abilities in terms of inference, reflection, creativity, and decision making was also very highly evident. The students’ level of problem solving before and after using Thematic Approach has a verbal interpretation of Developing to Approaching Proficiency. The study shows a significant difference in the students’ problem-solving skills before and after using the Thematic Approach. The result also shows that there is a significant effect on teacher’s utilization of Thematic Approach on the learner’s critical thinking Abilities. Thus, both hypotheses were rejected. The approach has the capacity to help students improve their critical thinking. By utilizing the approach, the students critical thinking, analytical thinking, and evaluating skills can be increased. It was also found out that there is no significant effect on teacher’s utilization of Thematic Approach on the learner’s problem-solving skills thus the third hypothesis was accepted. The lack of strong effect observed demonstrates that this approach may not be sufficient to produce evident progress in learners’ problem-solving skills. Moreover, the conclusion is drawn from the findings and the following recommendations are hereby given: the teachers may utilize different mathematical teaching approaches to easily understand word problems; learners really need to practice solving word problems in Mathematics and use their valuable time to improve their understanding of the different problems; and for further validity and reliability of the study, it is suggested to conduct the study in a larger group of respondents to determine if the results vary.