The Vampire Diaries star helped his former ladylove ring in her big 2-5 with a sweet tweet, writing Thursday, "Happy Birthday @ninadobrev !!! The world loves you!We all do;) Enjoy the moment, enjoy the day,enjoy the year!"
The TV co-stars hit the stage together at the People's Choice Awards Wednesday after they won favorite TV couple, and joked about their on-screen relationship and off-screen break-up, making light of what could have been a seriously awkward moment.
"We started dating in real life," Ian said after they talked about their on-screen romance. "And then we broke up in real life," Nina added.
"And yet our characters are still dating on the show," he continued, with Nina saying, "It's a good thing it's not awkward!"
After looking at the floor, they both held up the trophy, saying, "It's a good thing we have chemistry!," with Ian pulling Nina close and giving her a kiss on the cheek.
Julianne Hough also chimed in on the birthday wishes, posting a cute shot on Instagram of herself cuddled up with her BFF, with Nina holding a birthday cake.
"Happy Birthday my beautiful @ninadobrev you are kind, smart, adventurous, loving, honest, beautiful, mysterious, free, funny, and so on and so forth..... I am so lucky to call you my best friend! I love you so much... My sister! Happy birthday ya ol' fart!!! :) xoxo," she wrote.