The simultaneous effects of strain and grain size on carbide precipitation and sensitization development in 304 stainless steel having a constant carbon composition of 0.051% were studied. Three different grain sizes (150 μm, 40 μm, and 15 μm) were uniaxially deformed to 10% and 20% strain, and aged in the sensitization ranges of 625°C and 775°C. 150 μm samples were also strained to 20% in liquid nitrogen and aged between 0.1 and 10 h at 670°C. At 625°C, straining of the 150 μm grain size material produced a systematic increase in carbide precipitation, sensitization development, and desensitization. Transmission electron microscopy (TEM) revealed a greater continuity of carbides along the grain boundaries in the strained samples vs the unstrained samples. At the 15 μm grain size, these strain effects were found to be far less prominent with the sensitization-desensitization process occurring much faster, and accelerated at the higher aging temperature of 775°C, i.e. sensitization-desensitization envelopes were shifted to shorter aging times. Liquid nitrogen straining produced a sub-micron, 2-phase γ/α′, sub-micron grain structure which demonstrated an almost instantaneous sensitization-desensitization behavior, when aged at 670°C, which was predicted by extrapolation of the aging data for the larger range of grain sizes (∼ 15 to 150 μm) and the 625 and 775°C aging temperatures.