The current work studies evolution of microstructure of 17-4 PH stainless steel parts fabricated using laser powder bed fusion (L-PBF) process. 17-4 PH stainless steel gas-atomized powder of 13µm median size and water-atomized powders of 17µm, 24µm, 43µm median size were used to fabricate parts with L-PBF process by changing laser power and scan speed. Parts fabricated under all process conditions indicated that the phases present in X-ray diffraction (XRD) consist exclusively of martensite for gas-atomized L-PBF parts while austenite and martensite for water-atomized L-PBF parts. Furthermore, the phases present in the XRD were observed in the microstructures analyzed using scanning electron microscope (SEM). Additionally, the SEM analysis indicated that L-PBF parts fabricated with smaller particle sizes of gas-atomized powders (13µm) and water-atomized powders (17µm) produced dense L-PBF parts of ~97 percentage theoretical density and exhibited low porosity. Coarser size water-atomized powders of 24µm and 43µm median size produced L-PBF parts with 87-97 percentage theoretical density and exhibited variation in porosity. The results indicate that the mechanical properties of water-atomized parts were more sensitive to change in process condition and evolution of microstructure.