One Direction pin-up Liam, 19, and his childhood crush Sophia, 19, arrived hand-in-hand at the Sanderson Hotel in London, where the post-premiere celebration was taking place.
The cute new couple had coordinated in black outfits, Liam in a leather jacket, shirt and tie, and Sophia is a figure-hugging dress with purple panels.
To the disappointment of One Direction fans, Liam confirmed the relationship at a press conference for the band's film earlier in the week.
While the couple haven't been dating for very long, sources have said he has "really fallen for her. It's getting very serious, very fast."
Liam is so smitten he flew Sophia 5,000 miles to Los Angeles so she could be by his side at One Direction's final US concert on 10 August.
They weren't the only 1D couple attending the after party. Louis Tomlinson arrived with his long-term girlfriend Eleanor Calder, who showed off her long legs in a short blue dress.
Eleanor, a student at the University of Manchester, has been dating Louis since late 2011, and their romance seems to be going from strength-to-strength.
All eyes were on Zayn Malik and Little Mix's Perrie Edwards as they made their way inside the hotel. Following Perrie's appearance on the red carpet wearing a diamond ring on her engagement finger, fans were eager to catch a glimpse of the couple together.
They held hands and smiled as they arrived for the party, Perrie looking stunning in a embellished gown by Brazilian designer, Patricia Bonaldi.