The Lincoln County Humane Society in St. Catharines sent out a tweet Thursday saying the crustacean — dubbed Mickey the Lobster — died overnight.
The lobster's predicament became national news after it was discovered Wednesday in the parking lot in the southern Ontario community.
The humane society's executive director Kevin Strooband had said the restaurant doesn't serve lobster and it was suspected the crustacean was left there as an April Fool's Day prank.
The animal shelter had been making plans to send the lobster back to the Maritimes where it probably came from.
But now those hopes are dashed, although the humane society said on Twitter that it had received three offers to get Mickey home.
"Sad news, Mickey the Lobster has died, he died in peace and quiet over night, but had 3 offers to fly out east. Thanks for the well wishes," the tweet said.
Strooband said on Wednesday that the humane society had rescued the lobster by getting some salt water from a supermarket and putting the lobster into an aquarium.
He said an investigation into how the lobster ended up in the box in the parking lot was ongoing.