The main objective of the present study is to experimentally investigate and figure out the effect of deep cryogenic treatment in improving dynamic behaviors in terms of damping of a rotating shaft supported by rolling element bearings. An AISI 4140 steel for rotating shafts was selected for the experiments because it is the most widely used material in most industries for a wide range of applications such as machinery components, crankshafts, motor shafts, axle shafts, and railway locomotive traction motor shafts. Untreated, conventionally heat treated, deep cryogenic treated, and deep cryogenic treated and tempered shafts were used for the experiments to observe damping behavior changes of the shafts. Deep cryogenic treated and deep cryogenic treated and tempered shafts were cooled from pre-tempering temperature to -140 °C and held for tempering hold times of 12, 24, 36, and 48 hours. So, ten sets of shafts were employed for the experiment. The vibration data was captured for each of the shafts for five different shaft running speeds 600, 1200, 1800, 2400 and 3000 rpm. The results showed that damping ability of the deep cryogenic treated shaft at a hold time of 36 hours was superior to that of the others shafts.