The 48-year-old already has a close connection with his compatriot following his time managing the Croatia national team between 2006 and 2012.
Modric is still a key component at the Bernabeu under boss Zinedine Zidane, having started 18 games in all competitions this term, but Bilic has put the former Tottenham Hotspur midfielder at the top of his transfer wishlist.
Asked during a Q&A session which played he would like to sign, Bilic initially joked: "Lionel Messi", before adding: "But, there's one player that I would maybe get before Messi, and that's Modric. Of course [it's because he's Croatian] but I also get a discount!"
West Ham will have money to spend next summer after recently letting playmaker Dimitri Payet leave for Marseille in a deal worth £25m.