Strength and ductility are the most important physical properties in evaluating structural materials. Unfortunately, common strengthening strategies in most conventional alloys cause sacrifice of ductility inevitably. This trend is well known to ‘strength-ductility trade-off dilemma’. Recently, however, high-entropy alloy (HEA) which is constituted with several major elements is regarded as a good candidate that can overcome the strength-ductility trade-off. In the present study, we attempt to design the unique HEA microstructure with nano-thickness austenite film in hard martensite phase matrix. First of all, we made fully martensite HEA. Secondly, low temperature tempering process was performed for partial austenitization of the martensite. As a result, the HEA exhibited a novel ‘composite-like’ microstructure with metastability of the austenite film in martensite HEA matrix, which resulted in good ductility and strength balance. This result can provide a guideline on how to overcome strength-ductility trade off by tailoring microstructure in HEA.