In the present work, enhancement of heat transfer in a counter-flow double pipe heat exchanger (DPHE) is numerically investigated using a finite volume method. Thorough investigations have been conducted on the impact of dimple protrusions on the inner pipe of the DPHE, as well as the influence of Reynolds number (Re) and hybrid nanofluid on the heat exchanger’s performance. The findings are analyzed with regard to the coefficient of heat transfer, friction factor, effectiveness, and pressure drop. Our research indicates that an increase in Re leads to a rise in heat transfer, with a further increase observed when dimples are present on the inner wall surface. Additionally, the use of hybrid nanofluid alongside inner pipe dimples results in a boost in the heat exchanger’s effectiveness. However, when a hybrid nanofluid is used, the pressure drop as measured by the friction factor is higher.