The 29-year-old played both Tests in the series defeat to Sri Lanka following a seven-year absence from the squad, and he claims that Cook deserves credit for welcoming him back into the side.
"Alastair Cook has been brilliant," Plunkett told the Evening Standard. "When I came back it felt like I was still part of a county side, in terms of the way he spoke to me and the way he backed me. I bowled well at Headingley and that was because I felt so comfortable.
"When I was younger and in the team with people like Andrew Flintoff, Kevin Pietersen and Steve Harmison, I was a bit more timid. But now I feel like I belong. Everyone is encouraged to speak his mind and it feels as though everyone is backing each other."
Plunkett is expected to be named in the team to face India in the first of five Tests beginning next Wednesday at Trent Bridge.