It was Fallon's first time back on air since his mother, Gloria, passed away and he addressed his loss through tears.
"She was the one I was always trying to make laugh, and she was such a fan of the show and everything I did," he said, visibly upset.
"When we were little, my mum would walk us to the store - me and my sister - and we would hold hands," he continued. "And she would squeeze my hand three times and say, 'I love you,' and I would squeeze back, 'I love you, too.' Last week I was in the hospital, at her side. I grabbed her hand and I squeezed, 'I love you,' and I just knew we were in trouble."
Later, Fallon introduced Taylor Swift who performed 'New Year's Day' off her new album for the first time. She sang: "You squeeze my hand three times in the back of the taxi / I can tell that it's gonna be a long road."
The lyrics, which coincidentally fit perfectly with Jimmy's story of his mum, brought everyone to tears.
Following the show, producer and writer Mike DiCenzo thanked Taylor. "She sang 'New Year's Day.' No one had heard it. Suddenly she sings the line, 'Squeeze my hand 3 times in the back of the taxi.' I nearly gasped. Tears," he wrote. "I think everyone in the audience started sobbing," he said, as reported by E News.
"I could see Jimmy silhouetted at his desk dabbing his eyes with a tissue. We all lost it. It was a beautiful coincidence in a beautiful performance. 'Hold on to your memories, they will hold on to you,' Taylor sang. That hug between Jimmy and Taylor after the song was 100% real emotion. Whatever you think of Taylor, she did something beautiful for Jimmy and our show today, and we're forever grateful."
This article previously appeared on marie claire.