Battery thermal management system (BTMS) is a hot research area for electric vehicles (EVs). Common BTMS schemes include air cooling, liquid cooling, and phase-change materials (PCMs). Air cooling BTMS is widely used in EVs because of its simplicity, high efficiency, and low cost. However, past air cooling BTMS research focused on inlet flow, air channel design, and battery layout. Few studies have focused on improving the heat transfer efficiency of battery packs. This paper aimed to improve the heat transfer efficiency of air cooling BTMS by using herringbone fins. Both inline and staggered arrangements of lithium-ion cells were considered. Moreover, the effects of transverse pitch, longitudinal pitch, fin height, fin number, and inlet velocity were examined. Installation of herringbone fins with optimal values of parameters caused a decrease in average temperature of cells by 3.687 K in the inline arrangement and 4.15 K in the staggered arrangement. Furthermore, a significant improvement in temperature uniformity was also observed. The simulation results will be helpful for the design of air cooling BTMS.