Modular tray support (3), suitable for placement in a sterilization chamber (2) of an autoclave (1) for sterilizing surgical/dental/veterinary instruments, for supporting sterilization trays (12) and/or cassettes (13) containing said instruments to be sterilized, characterized in that it is adaptable to the dimensions of the cassettes/trays to be sterilized. Autoclave (1) comprising said modular tray support (3).