The first post came from Scott, 42, who shared a video packed full of photos and even a few short clips of the pair, beaming in every photo.
While some of the photos were selfies, others came from red carpet events or outings with family and friends.
"How time flies when you’re having the best time of your life," he wrote in the caption. "Who would’ve known that exactly one year ago my life would change forever. When I count my blessings, I count you twice."
Not long after, Deschanel, 40, shared her own tribute, including two photos of her and Scott cuddled up.
In the first pic, the actress sat on her boyfriend's lap while they donned festive holiday headbands, and in the second, the two posed for a picture while soaking up some sun outside.
"One year ago today I met this kind, caring, hilarious, generous, creative, nerdy, handsome and all around incredible human," Deschanel reflected in the caption. "I am so grateful for every smile, kiss, hug, snuggle, laugh, scrabble game, escape room, breakfast, lunch and dinner we share together."
She concluded: "Even during the weirdest year for humanity I want a million billion more with you."
"It has not been difficult at all, it's actually been a blessing," he said of being home with Deschanel, saying that because he's often on the road, "now being here, being together all the time has been fantastic."
Scott told the hosts of "The Talk" that if he had to choose someone to be stuck at home with, the "Elf" star is "the one."
"... She can cook, she's a musician, so there's so much music in this house -- she was playing the piano last night, we were singing together," he added.