Frank Calderon, 16, a junior at Pensacola Catholic High School in Florida, posted video of the gesture to his Instagram and it's been making the rounds on social media.
The touching video, which was taken on Oct. 25, 2019, shows him walking into the stands with the flowers, wrapped in pink tissue paper, as spectators cheer and his Crusaders teammates rush the football field to play in a game against Choctaw High.
In the video, Frank Calderon, wearing a No. 20 jersey, hands his grandmother, Amparo, the flowers and gives her a big hug before saying, "I love you, Grandma." The video then show her wiping tears from her eyes.
Karla Calderon, Frank's mother, said the entire team had also worn pink socks for the October game in honor of cancer awareness. She said that while the family knew of Frank Calderon's plans, his grandmother did not.
On Thursday, Karla Calderon expressed gratitude for the support they'd all received since the video was posted.
"Our family is so thankful for the prayers and good wishes," she told ABC News Thursday.
Frank Calderon told ABC News on Thursday that his grandmother had cared for him since he was born and that now he was caring for her, even going with her to chemotherapy treatments.
He also said the message behind the video was clear: "Family always comes first."
"She's always been there for me," he said. "She's a strong woman. She's beat [cancer] once. I think she can beat it again."
His team won the game that day, 45-35, and finished the season undefeated. In his video, he dedicated that winning season to his grandmother.