Packaging for prosthetic heart valves including an assembly for stabilizing dry prosthetic tissue implants such as heart valves during storage. The packaging assembly includes a primary sterile barrier feat permits gas sterilization of the tissue implant, and a secondary sterile barrier that prevents oxidation of the implant during storage. Tissue heart valves are placed inside, an inner tray and sealed with, a gas-permeable lid. The inner tray is placed within an outer sterile barrier and the assembly is sterilized. The outer sterile barrier may include a double seal so that a first gas-permeable seal can be closed for sterilization, after which a second gas-impermeable seal is closed to seal out any further oxygen, contact with the tissue implant Alternatively, the inner tray is placed within a sterile pouch and the assembly gas-sterilized, and then the entire assembly is placed within another pouch that provides an impermeable barrier.