Kai shone on stage as she donned a dazzling sequined dress during her grandfather's victory speech in the early hours of Wednesday morning.
During this election cycle, she has become a social media sensation, largely due to the quality of her golf game.
Following her appearance on stage, Kai took to social media to post a doting photo of her and her grandfather.
'No one works harder or cares more about the American people. Congratulations Grandpa, I love you!' she wrote.
Like Melania, Kimberly was in attendance on election night and graced the stage with Trump, but was not in the 'squad' photo Kai shared.
The former Fox News host has been dating the president-elect's eldest son, Don Jr, since 2018, following his divorce from first wife Vanessa. The couple got engaged on December 31, 2020 but it wasn't made public until January 2022.
She is the ex-wife of California Democratic governor Gavin Newsom and has since become a prominent member of Trump's close circle and campaign.
By contrast, Elon Musk was not on stage with the rest of the family when Trump gave his victory speech, but did make it into Kai's squad photo.
Holding his son X in his arms, Musk beamed as he stood next to Lara Trump - a rising star within Trump's inner circle.
Musk had earlier revealed he would be at Mar-a-Lago with Trump and his allies as the results started rolling in, after becoming one of the Republican candidate's most outspoken allies and generous donors in 2024.
He publicly backed Trump after he survived the July 2024 assassination attempt.
'I love that Elon is family now,' one supporter wrote on Kai's photo.
'Did Grandpa just adopt a son?' another added.