Additive manufacturing (AM) of high-entropy alloys (HEAs) is a new challenge in the Material Science and Advanced Manufacturing fields. In the AM processing procedure, heat treatments after fabrication are often beneficial to stabilize microstructure and properties, while limited reports are available for AM HEAs. In the presented study, the effect of a post-printing heat treatment at 400–1000 ℃ for 24 h and for 21 days on the changes in structures and phase compositions of an AM CrFeCoNi alloy prepared by the laser powder bed fusion AM technique is presented to better understand a heat treatment-microstructure-property relationship of the AM HEA. Heating up to 600 ℃ demonstrated the polygonization process in the alloy. Grain growth was observed in the alloy upon heating over 700 ℃, while a preferred texture is observed along the build direction after annealing at 900 ℃ for 24 h. The formation of the secondary phase was revealed, and it is associated with the impurities of the initial CrFeCoNi powder. The AM CrFeCoNi system demonstrates excellent phase stability inthe solid solution for all annealing temperatures.