The commuter and his reptilian mask, which was wrapped around his neck and mouth, were seen on a bus from Swinton to Manchester on Monday.
One passenger, who asked not to be named, said she initially thought the man was wearing a “funky mask” before she spotted it slithering over the hand rails.
She said she found the incident “really funny” and that the animal did not seem to be bothering any of her fellow passengers, telling PA: “No-one batted a eyelid.”
Pictures showed the man was not wearing a mask under the snake.
Using a face covering on public transport is mandatory in the UK, except for those who are exempt for reasons of age, health or disability.
A Transport for Greater Manchester spokesperson said: “Government guidance clearly states that this needn’t be a surgical mask, and that passengers can make their own or wear something suitable, such as a scarf or bandana.
“While there is a small degree of interpretation that can be applied to this, we do not believe it extends to the use of snakeskin – especially when still attached to the snake.”