She called off the performance on her Beautiful Trauma tour in Sydney after coming down with a chest infection.
The 38-year-old had been snapped by paparazzi photographers enjoying a day with her family on a beach in Byron.
Speculation followed about why she'd cancelled prompting Pink to respond on Instagram.
Next to a photo of herself and her daughter, Willow, she wrote: 'I scheduled this tour meticulously, trying to do what was best for my children, while also putting on the best and most physically demanding and beautiful show of my life."
Justin Timberlake then came to her defence, commenting on Pink's post, calling her "the REALEST."
"As an artist who has had the fortune of sharing the stage twice on tour with this incomparable BADASS (once with 'NSync and once as a solo artist), I'm here to tell you that you won't find a harder working, more authentically talented, and more thankful for her place on that stage and her fans than this woman."
The 37-year-old went on to say he related to what Pink was going through - as he struggles with his own health.
"And NOW... as a parent on tour as well, and an artist who LOVES their fans just as much and wants to give them an unprecedented experience... AND is currently battling an injury, a sinus infection, and trying to be the DAD I want to be too??
"I say HATS OFF to you, my friend. I don't know how Moms/Artists like you exist."
He criticised the paparazzi photographers who took the beach pictures and wished Pink a speedy recovery.
"Go make up some fodder about somebody who's half-assin' it. NOT a real one.
"Wishing you full health and speedy recovery, Pink! Shine on, sis!!!!! -- JT," he ended.
Pink originally called off the tour date on 3 August posting an apology on Twitter and then asking for recommendations on where to get wellness shots and juices in Sydney.