In this study, the effects of hot dip galvanizing on the fatigue strength of raw AISI 4340 and ion nitrided AISI 4340 steel in laboratory air atmosphere were studied. While the galvanizing process was applied at 451 degrees C for 1 min, the ion nitriding process was applied at 500 degrees C for 2 h using NH3 gas. It is known that hot dip galvanizing reduces the fatigue strength in steels. While the reduction in fatigue strength after galvanization was 36.7% in the hot rolled AISI 4340 steel, it was reduced to 7% when hot dip galvanizing was applied to the ion nitrided AISI 4340 steel. The use of ion nitriding before hot dip galvanizing has limited the decrease in fatigue strength caused by galvanizing. On all ion nitrided specimens, both hot dip galvanized and not, fatigue crack initiation was moved towards to core thus increasing the fatigue strength.