The special dress, available in Japan, promises "round-the-clock protection against the effects of gravity".
Christened Floral Goodnight Bra, and known in Japanese as the Kahei Oyasumi Bra, it also offers "much-needed support as you sleep".
Kaku Nishioka, who sells the bra at his Tokyo shop, said: "It is something that not many men are aware of.
"But if a man has good pectoral muscles he is at just the same risk as a woman of having them gradually stretched and left out of shape.
"A man who wears this bra to bed at night will find everything is held firmly in place and looking good the next day."