Tomkins spent 19 years with West Ham, developing through their youth academy, before leaving in 2016.
Tomkins has now joined Palace, and he has gone on to face West Ham on multiple occasions.
The centre-back is set to face his former side once again at the weekend, but he insists that he has no divided loyalties.
“I try and leave it to the side that they're my old team now," he said. "My first few times playing them was a bit strange, obviously. I was there for 20 years.
"Now, it seems like they're just another team and a team that we want to get points from. I always get a warm welcome back there, which is nice. But it's an extra incentive playing against your old team. We're looking forward to it. I'm looking forward to it, but I look forward to every game.
It's changed a lot since I was there. The year they moved stadium was the year I left, they moved training grounds as well. Everything changed just as I left. So even though I'm playing against my old team, it doesn't feel like it because you're not going to Upton Park or places like that. It does feel a bit different there now but it's obviously a club I still look at, keep an eye on the results of and stay in touch with a few people.”
Tomkins made 243 appearances for the Hammers during his time at the club.
Since leaving he has become a regular in Palace’s side, and looks likely to start at the weekend.
Tomkins’ task of stopping his old side will not be an easy one, as they have been in good form of late.
West Ham have won back-to-back matches for the first time since 2017 in midweek.
Palace, meanwhile, were beaten by Brighton & Hove Albion after putting in a terrible performance at the Amex Stadium.