The mixed method research determined the effect of Problem-Based Learning (PBL) on the problem-solving and social skills of 81 Fourth Year students of the Integrated Laboratory school (secondary) of the West Visayas State University of the school year 2003-2004. The data needed of this study were gathered through the researcher-made, injury validated questionnaire on social skills used both in the pre- and post-test and a rubric for problem-solving adopted from the North Western Regional Educational Laboratory (NWREL, 2000). The data from the questionnaire on social skills were augmented by the observation checklist Adopted from Goldstein & Pollock (1998), still pictures, and video recording. Mean, standard deviations, t-test for dependent and independent samples, and Pearson`s r were the statistical tools used. Significance was set at .05 alpha level. The students` problem-solving skills as measured by the rubric provided the qualitative data for the study. These were augmented by the students` journals, interviews and observations. Findings of the study showed increases in problem solving and social skills of students exposed to PBL. The two groups were comparable at the start of the experiment in their problem solving and social skills. In terms of pretest and posttest problem solving and social skills results within groups, significant differences were found between the two groups. A positive and significant correlation was found between the pretest problem solving and social skills in favor of the experimental group. However, there existed a positive but not significant relationship in the mean gains problem solving and social skills. It was concluded that PBL could effect significant improvement in problem solving and social skills than traditional teaching methods. Thus by all indications, PBL promises great potential as an alternative teaching method in teaching high schools mathematics and perhaps other courses in the tertiary level. These are reflected by the students` journals, interviews, group discussions and teachers` and observers` observations and journals.