Trinidad & Tobago international John joined Crystal Palace this week after turning down a two-year deal to remain with the Saints.
And Pardew admitted that John's decision to leave, after he had previously expressed intentions to the contrary, has been difficult to swallow.
"I'm not best pleased if I'm honest," he told the Southern Daily Echo. "He kept making excuses about his agent and because of the loyalty I thought he had to Southampton and the character he had I assumed this was correct. I think he even mentioned that his agent had some family troubles.
"You think that everything is fine because he never asked us for more money, never implied that there was a problem and then he came to see me on Thursday I think and said he had an offer from the Championship and he was going to leave.
"My reply was 'see you later'."