The British royal was meeting with Games organisers at the Emirates Arena with the Duchess of Cambridge, when he greeted a little girl and her mother.
Shona Ritchie, 4, had been waiting for the prince with her family, and had wanted to ask William for a kiss all morning.
However, when the prince leaned over to accept her kiss, she became embarrassed and pulled away twice at the last second, prompting laughter from the future King.
"She's been dressed up like that since 6am today and we've been here waiting since 9," Mrs Ritchie told The Guardian.
"But when she finally plucked up the courage to ask him, she got really shy and pulled away. As he leaned in to kiss her on the forehead she pulled away and got really shy.
"This is the quietest she's been all day."
The Duchess of Cambridge later spoke to Shona, who gave her a red flower she had picked from her mother's vase.
Mrs Ritchie added: "She said Shona looked very pretty and asked her if she had picked the flower from her garden, but Shona told her she got it from my vase in the house and she thought that was very funny."
The royal couple visited the new Sir Chris Hoy Velodrome, where they watched and cheered on riders during a practice session in the stadium.