The father-of-two rewatched Nightbirde's audition, who got his number 1 spot, for the first time since her death earlier this year and couldn't help but cry alongside co-star Terry Crews.
WATCH: Simon Cowell cries whilst remembering Nightbirde
"You know, this is difficult. I haven't been able to watch this since she passed," he told Terry as they began to watch the star, whose name was Jane, sing her original song titled It's Okay, which talks about her cancer battle.
"What was so special about Jane in my opinion was that she was always optimistic, but of course, she recently passed away, which makes this tough. All she ever kept talking about was the music," Simon continued to say whilst watching the clip.
Simon and Terry became incredibly emotional whilst watching Nightbirde's audition
Towards the end of the video, it all got a bit too much for Simon and Terry, and with tears in their eyes, Simon could be seen pleading with the cameramen to give him "two secs" to recover.
"The amazing grace she showed amongst the adversity, it was a lesson for all of us," Terry told Simon.
Simon added: "The last time I saw her, she did say what that moment meant to her. All these years she had tried to get recognition as a songwriter, as a singer, and in an instant, everything changed for her.
"I promise you, so many people come up to me and talk about what she did, giving people hope and perspective and that lyric of that song and you know… she typifies what the Golden Buzzer is all about."
Simon took to Instagram to share a special tribute to the AGT contestant
Taking to Instagram, Simon shared two beautiful black and white photos of him alongside Nightbirde, and wrote: "@_nightbirde was one of the most inspirational people I have ever met. She was so incredibly brave and I am very grateful she chose @agt to show the world her talent. I will never forget this moment."
Nightbirde, whose real name was Jane Kristen Marczewski, sadly passed away in February this year after a four-year battle with cancer.
The 31-year-old auditioned for America's Got Talent 2021 and was awarded Simon's coveted Golden Buzzer.
Sadly, Jane never got to compete on the show as her health took a turn for the worse.