The England midfielder had four seasons at Upton Park before leaving for Spurs in a £6m deal 18 months ago and he was a big fans' favourite at the club.
Parker was named 'Hammer of the year' three times, and footballer of the year by the Football Writers' Association in his final season even though West Ham were relegated, but he was booed throughout his first appearance at Upton Park since leaving.
"I didn't expect the West Ham fans to boo me and obviously it was a little bit upsetting," said Parker, who played 113 times for West Ham.
"I don't know why (they did it). I don't know if it's because I went to their local rivals... I'm not sure, but I just would have liked to think that maybe I would have got a better reception after what I did in my time here.
"I loved (Upton Park), the fans, and I loved the club.
"I had four fantastic years here and it will always be a club with a massive place in my heart. I was looking forward to coming back and I couldn't wait to go out there and play so I was disappointed (to be booed)."
Tottenham last week