On Friday, Mendes, 25, shared a photograph in honor of the couple’s one-year anniversary.
“365 days. i love you,” Mendes captioned the shot, which shows the Riverdale stars kissing on a boat with a stunning view of the sun setting above water behind them.
Melton, 28, also celebrated their big day by posting a shot of them cuddled up together on another boat ride with their hair blowing in the wind.
“I love you,” Melton wrote.
Back in May, Mendes opened up about their romance telling Entertainment Tonight at the premiere of Melton’s film A Sun Is Also a Star that “[h]e does [write me love letters].”
“He’s a hopeless romantic, for sure,” Mendes said.
Melton further explained the sweet gesture during an episode of PEOPLE Now that same month, saying, “It’s just the simple things, you can just say something like ‘I’m thinking about you.'”
“There’s just something special about writing it, folding it up and putting it into the envelope and finding a stamp,” Melton said.
The actor also revealed his ideal date night.
“Just Postmates and watching TV,” Melton explained.
The couple, who attended the 2019 Met Gala together, confirmed their romance in October 2018 with a PDA-filled instagram courtesy of Mendes.
“Mine,” she captioned the photo, which featured the couple locked in an embrace as he kissed her forehead.
Melton later tricked fans on Valentine’s Day by showing off a “Cami” tattoo on the left side of his chest, though Mendes later clarified it was fake.
“The tat is fake lol thought it was obvious from the sticky patch around it but guess not,” she wrote on Twitter.