Precipitation hardenable stainless steels have become a material of choice for many advanced engineering applications that require high strength and excellent corrosion resistance. Solution treatment temperature is an important parameter that influences the prior austenite grainsize and retained austenite content in this type of steels. Solution treatment has been carried out in a 12Cr–10Ni steel at treatment temperatures ranging from 750 to 1000 °C at 50 °C intervals. Aging was carried out on two sets of solution-treated samples at 250 and 500 °C. Charpy impact tests at room temperature and 77 K were carried out on solution-treated as well as aged samples. Measurement of retained austenite, prior austenite grainsize, and EBSD analysis were carried out to explain the observed phenomena. Solution treatment temperature is observed to have only feeble effect on impact toughness and hardness; however, it considerably affects the content of retained austenite. The aging temperature and thereby the precipitate size were observed to be the major factors that influence cryogenic impact toughness for 12Cr–10Ni steel.