Through the learning of physics, students will acquire problem solving skills which are relevant to their daily life. Determining the best way in which students learn physics takes a priority in physics education. The goal of the present study was to determine the effect of problem based learning strategy on students' problem solving skills and its role in building their motivation. A quasi-experimental research method was adapted. Problem solving inventory test and motivation scale were used to collect data. Subjects included were 81 grade 12 students taken from Wachemo Preparatory school. There was a mean difference between comparison and experimental groups. The covariate analysis shows that the difference was statistically significant with effect size above average. However, there was insignificant difference in motivation to learn physics. The study suggested that to improve students' achievement, schools must adapt the PBL method carefully. However, students' motivation to learn physics remains vague.