This study aims to determine the effectiveness of Project Based Learning (PjBL) on students' learning outcomes for sub material the role of viruses in class X of SMA Islam Bawari Pontianak. The research method used was a quasi-experimental design with nonequivalent control group. The sample was XA class (control class) which consists of 31 students and class XB (experimental class) which consists of 32 students, while the sampling wasintact group. The instrument used was a multiple choice test which consist of 20 items. From the analysis of the data, obtained an average score of posttest results of students in the experimental class which was 17.75, while the average score of posttest in control group was 15.64. Based on the analysis of U Mann Whitneytest showed that Zcount ≤ Ztable (-3.78 ≤ -1.96) that it can be concluded that there is a difference in students' outcomes whom were taught by using Project Based Learning (PjBL) with those whom were taught by using conventional teaching. For effect size is 0,75, the category when effect size at convertation is medium. Based on the value of Effect size, it is known that Project Based Learning (PjBL) contributed 27.34% on the learning outcomes.