Bindi Irwin has admitted she struggled to look at her brother's shirtless photos.

The conservationist described seeing Robert's stripped-down photos as "rough".

Robert, 21, recently posed in only a pair of underpants for Australian underwear business, Bonds - and the resulting ad campaign left his sister feeling uncomfortable.

"Wow. I will say there are some things as his sister that I can't just unsee," Bindi, 26, joked during an interview with the Not Gonna Lie with Kylie Kelce podcast that aired this week.

She pointed out Robert had also opted to go shirtless for the recent announcement he would be competing on Dancing with the Stars.

"When he did the Dancing announcement, he was also just shirtless, and he recently did his, like, Bonds commercial where he was just in his underwear, and it is, it is rough."

However, she said, she was happy for her brother to do whatever it took to get their shared message of caring for the planet and its animals out to the public.

"We have a charity called Wildlife Warriors," Bindi said, "and watching him grab people's attention in such a big way and then pivot and say, 'Here's what we do. Here's our work. Here's our dedication to wildlife and conservation, and you can get involved.' It is wonderful and extraordinary to watch him just shine."