Custom 465 is an advanced precipitation hardened martensitic stainless steel exhibiting a combination of high strength, high fracture toughness and good corrosion resistance. This steel is recommended for use in hydrogen atmospheres, yet only little research has been published on hydrogen behavior in this alloy. Here, the diffusivity, solubility and average detrapping energy for hydrogen were compared in various thermal conditions (solution annealed, H900 and H1000), employing electrochemical permeation and thermal programmed desorption measurements. It is suggested that reversible (low energy) traps in the H900 and H1000 conditions, associated with (semi) coherent eta-Ni3Ti precipitates, are responsible for the high hydrogen solubility and low diffusivity. At the peak of coherency of the precipitates in the H900 condition, higher solubility and lower diffusivity and detrapping energy were measured. The value of the diffusion coefficient is found to change during different stages of charging and discharging, depending on the level of occupancy of the reversible traps. (C) The Author(s) 2018. Published by ECS.