Project-based learning (PBL) is increasingly recognised as a transformative alternative to traditional, instructor-centred education, fostering positive student attitudes towards learning. However, public schools in Pakistan largely adhere to conventional teaching methods, contributing to poor mathematics achievement and negative student attitudes. In this study we explored the potential of PBL to enhance attitudes and mathematics performance among students in Pakistani public schools. Grounded in constructivist learning theory, which emphasises active, experiential learning, we employed a quasi-experimental design in this study. The experimental group received PBL-based instruction, while the control group was taught using traditional methods. Pre-intervention and post-intervention assessments were conducted for both groups to measure attitudes and achievement. Quantitative data were collected through an attitude scale and an achievement test, and qualitative insights were gathered via structured interviews. Statistical analysis of the quantitative data, using the Wilcoxon signed-rank test and independent sample t-test, revealed a significant improvement in the experimental group's attitudes toward mathematics learning (z = -4.570, p < 0.001) and achievement (p < 0.001). Thematic analysis of qualitative data further highlighted that PBL positively influenced students' perceptions and success in mathematics while receiving favourable feedback from both teachers and students. These findings underscore the potential of PBL to improve mathematics instruction and student outcomes in primary education. Future research should examine the applicability of PBL across diverse school settings, grade levels, and age groups to establish its broader efficacy in varied educational contexts.