Wendy Foley made desperate calls to the police and RSPCA but was told she would have to wait until the next day before someone could come to take away the 5ft reptile, thought to be a corn snake.
Mrs Foley, 51, who lives with her sons Tom, 18, and Ed, 21, at Farm Hill, Exwick, Exeter, discovered the snake curled up on her wet washing inside the machine. She thinks it probably crawled in when the door was open and survived a wash.
She said: "The washing had been through a full cycle and was ended, so I was going to take it out and put more washing in.
"I opened the glass door at the front and I saw something. I took it to be part of a pair of jeans and then I wondered if it was a toy snake that children use. But then it poked its tongue out at me.
"It was horrible and quite big. It was just sitting there on the washing. I don't know if it had been through the complete cycle or not. I screamed and screamed — I was terrified."
Mrs Foley said she first called police but she thinks they reacted like it was a hoax call.
She said: "I called the RSPCA and they said they would send someone but it wouldn't be until the next day. The boys and I waited outside the house for a while because we were so scared. Then they went to bed and I just sat on my bed all night absolutely petrified.
"I kept thinking that it would get out and also that there could be more than one in the house. I hate snakes. They scare me and I've absolutely no idea where this one came from."
A Devon and Cornwall Police spokesman said it has logged the call and referred the matter to the RSPCA.
Exeter RSPCA spokesman Jo Barr said its team had taken the snake away. It was believed to have been a corn snake. She said: "The caller said the snake was in good health, not injured and was confined so it was not sick or in danger and an officer was sent out first thing in the morning. We do have officers working around the clock but their priority has to be animals which are badly injured or in need of urgent rescue."
Cherry Keehner, of Heavitree's Tiny Boa reptile shop, said corn snakes were not poisonous can bite if scared.