The Baggies were given the lead by Jay Rodriguez's goal early in the second half and held on until Jordon Ibe equalised 13 minutes from time. Junior Stanislas then won the game for Bournemouth with a late free-kick to leave West Brom ten points adrift of safety.
"It's really difficult to take," Pardew told WBA TV. "It's heartbreaking for everyone - the fans, the staff and particularly the players, who did not deserve that.
"The gameplan and the execution of the gameplan I could have no complaints about. It's very difficult to talk to the players after an effort like that - their application and their fight was commendable.
"They did not deserve that outcome, they really didn't."
Pardew also cursed West Brom's luck as they lost captain Jonny Evans just before Bournemouth scored their opening goal. Evans missed West Brom's 4-1 defeat to Leicester last weekend through illness, and had to be substituted in the 77th minute on Saturday.
"We did not expect to lose Jonny but he has been ill and his levels must have been down because he was cramping up and struggling to run," said Pardew. "That came just before Bournemouth's first goal and certainly didn't help us.
"Without that I think we would have gone on to win the game, but it's the sort of thing that happens to you when you're in our position."