The Science education curriculum in the Philippines has shifted from inputs-based to outcomes-based education, putting the learners at the core of the instruction. Hence, educators continue to innovate ways on how to engage the learners into relevant and responsive science instruction. Further, the implementation of the K to 12 curricula brings a paradigm shift in education in terms of pedagogy, assessment, and outcomes. Within-group quasi-experimental research attempts to test the effects of the Jigsaw II strategy on the students' science achievement. A total of 51 Grade 9 students in a government-run secondary school in Zambales, Philippines, participated in the study. Results revealed that the class improved from "developing" to "proficient" level in their science achievement after the implementation of the strategy. It found out that the Jigsaw II strategy had a significant effect on the science achievement of the learners. The study recommends the use of the instructional strategy in enhancing students' performance. The strategy may be applied in other science topics to see its effectiveness further. This paper likewise contributes to the literature on the effectiveness of the Jigsaw II learning strategy in science teaching in the Philippine context.