During ET's interview with the 50-year-old Pose star at the 2019 American Music Awards, Eilish came over to excitedly give Porter a hug.
"You were unbelievable this afternoon!" Porter told Eilish of her rehearsal performance as they embraced. "... You look amazing."
"Look at you! You look incredible," the 17-year-old singer responded.
Following the sweet moment, Porter went on to gush over Eilish's talent.
"Oh my God. I saw her perform today cause I was here," Porter told ET's Keltie Knight. "It's really lovely to see the new generation of music folks... I have mine, [but] you get to a certain age and you stop following everything and everybody, so it's always great to be in these moments to see what's hot."
Porter also praised his friend, Taylor Swift, who took home the Artist of the Decade award at Sunday night's ceremony.
"My sweet Taylor. I just love that she is her own woman," Porter said. "I love that she doesn't take no mess from nobody. She understands her power and she sits in that."
"It's amazing to see somebody so young be able to do that," he continued. "She's talented and she understands her worth and I love that."
"It doesn't really matter who wins it, because... to be even nominated at all, to be in the realm of the GRAMMYs in any sort of way, is really indescribable," she said. "I've been watching the GRAMMYs my entire life... and it's insane."
"Even to be [at the AMAs], at the rehearsals the last couple of days, I'm looking at the row that I'm seated in, and it's like every single person that I grew up watching on TV in that row, and I'm in that row," she added.
Watch the video below for more of ET's interview with Eilish.