The Reds centre-back is among the favourites to land the accolade following an outstanding campaign for the Premier League leaders.
While Sterling has scored 15 league goals for City, their rivals for the league crown.
"I voted for Raheem Sterling," Van Dijk told reporters, as per The Guardian.
"I did what I thought and I thought he deserves it. He's had a fantastic season.
"I could have voted for Bernardo Silva as well and another couple of players from Manchester City. But I'm just being honest. I think he has improved a lot as a player."
PFA rules prohibit players from voting for their teammates.