Masked raiders broke into a young woman's house as she slept and threatened her with a kitchen knife.
The three struck in Harrington Avenue, Blackpool, at about 0300 BST on Wednesday.
They searched the 22-year-old woman's bedroom and threatened to hurt her if she moved, police said. They fled with several electrical items.
A 20-year-old man has been arrested on suspicion of aggravated burglary and released on police bail until 23 June.
Pc Katherine Ward, of Lancashire police, said: "This was a violent crime in which the female victim has been left shocked and traumatised.
"We are appealing for any witnesses to come forward - we are particularly interested to hear from anyone who saw any vehicles in the nearby area or any suspicious activity at the time of the incident."