Abstract This study examines mass and heat transfer in a permeable ternary nanofluid flow over a stretching sheet, considering the combined effects of a chemical reaction, Joule heating, an exponentially space-dependent heat source, and an inclined magnetic field. Three types of water-based nanofluids are analysed: mono (Cu), hybrid (Cu + Al 2 O 3 ), and ternary (Cu + Al 2 O 3 + Ag). The governing nonlinear partial differential equations are reduced using similarity transformations and solved numerically via MATLAB’s BVP4c method. The results reveal that ternary nanofluids exhibit superior thermal performance, with significantly higher temperature profiles compared to mono and hybrid nanofluids. The influence of key parameters is also investigated. Increased suction and velocity slip reduce thermal and concentration boundary layers, while higher Biot numbers and heat source intensity enhance temperature profiles. Additionally, Joule heating and magnetic field inclination intensify the heat transfer rate. These findings provide valuable insights for optimizing thermal systems in applications such as solar energy collectors, thermoelectric devices, and chemical processing industries.