RM Sotheby said the price is a world record for a Porsche 356.
The custom painted 1964 model had never left the Joplin family, which decided to lend it to the Rock and Roll Hall of Fame in Cleveland.
The final selling price ended up being triple the pre-sales estimate.
Joplin - who sang the now famous "Oh Lord, won't you buy me a Mercedes-Benz" – had the original white finish painted with a red mural including images of butterflies, birds and pictures of her band.
Joplin regularly drove the car and it was found parked outside the hotel in Hollywood where she died from a drug overdose in 1970.
"Janis Joplin's 356C is without question one of the most important Porsches of all time," said Ian Kelleher, managing director of RM Sotheby's West Coast Division, when he announced the car was going up for auction.
Janis Joplin'S 1964 Porsche (AAP) Source: AAP
"It's a fantastic automobile that transcends art, pop culture and social movements, and is as groundbreaking and stunning as the renowned singer was herself."
Michael and Laura Joplin said they plan to use the money from the sale of the car to support social programs in Janis's memory.
