Automotive heat pump (AHP) systems have been recently employed in electric vehicles where waste heat is limited. Due to its impact on global warming, the use of R134a was restricted, and R1234yf has been regarded as its best alternative for automotive air conditioning systems. The AHP systems using R1234yf perform poorly, and a remedy to this problem may be the use of an internal heat exchanger (IHX). This study aims at evaluating and comparing various performance parameters of an experimental AHP system using R134a and R1234yf with and without an IHX. The findings reveal that the R1234yf system with IHX provided on average 13.9% lower heating capacity but 7.8% higher COP based on total power consumption relative to the R134a system. Moreover, for 5 degrees C air inlet temperature, the R1234yf system with IHX yielded on average 22.3% less exergy destruction rate per unit heating capacity compared to the R134a system.