Physical Science involves study of non – living things. Since it is being offered among non–majors, teachers surmount challenges particularly appreciation for scientific inquiry. Likewise, De la Salle Lipa exposes students to transformative learning approach to attain its expected La Sallian Graduate Attributes and one of which is being a critical thinker. Thus, this study assessed the extent by which critical thinking skills were enhanced through reflective journal writing. Using the descriptive instructional method of research, this study used the Provus Evaluation Model in its approach to assessment of major variables concerned. Purposive sampling technique was used among 80 Second Year Bachelor of Science in Accountancy and Bachelor of Science in Legal Management who were enrolled during the second semester of School Year 2011 – 2012. Data and other information needed were gathered through questionnaires, informal interviews, observations, documentary analysis and the use of triangulation of data. Results revealed that indicators of critical thinking skills have been found to have been “enhanced to a great extent” However, in consideration of the Total Quality Assurance (TQA), it was found that gap existed between the mean assessment of the respondents and the intent of TQA. In consideration of the findings, an enhancement guide has been proposed to introduce and implement reflective journal writing among non – majors in college or universities’ quest to continuously improve instructional program and attain total quality assurance.