Some have criticised the change while others are saying it makes him "look 17 again", dating back to his formative years at Sporting.
Cristiano Ronaldo, who has regularly kept his hair in a topknot since joining Juventus, left it untied and some of his locks come down to the side of his face.
With over 4 million likes in an hour since posting, his current and former teammates have already had their say in the comments section.
Real's Marcelo and Juventus winger Douglas Costa found it amusing, while UK broadcaster Piers Morgan and Cristiano Ronaldo's sister Katia were among those happy with it.
See and judge for yourself:
While Cristiano Ronaldo has resumed first-team training in Turin, the 35-year-old is also enjoying his time on social media, with the 2019-20 Serie A season expected to resume sometime in June.
As we covered last week, the league will remain suspended until June 15 at the earliest.
In contrast, Italy's minister for sport Vincenzo Spadafora said the campaign could resume on 'either June 13 or 20', after the coronavirus pandemic suspended play in early March.
A concrete decision on how things move forward is expected this Thursday, as Italy's top-flight are hopeful of returning sooner rather than later - especially after Germany's Bundesliga resumed on May 15.
Spain's La Liga, where Cristiano Ronaldo spent nine years, can resume as early as June 8 while the UK's Project Restart plans are hopeful for a mid-June resumption in the Premier League too.
Cristiano Ronaldo passes time before season resumes
Cristiano Ronaldo has scored 21 goals and created three assists in 22 league games so far this term, so is determined to regain his match sharpness as quickly as possible.
Nonetheless, he's also creating that balance by enjoying himself off-the-pitch during these unprecedented times - having fun with his family and posting various clips in recent days.
Yesterday, Cristiano Ronaldo posted a thoughtful caption on Instagram alongside a picture of him at training which read,
"Positive thoughts...always! 💪🏻"
He and his Juventus teammates will certainly need positive thoughts, if they are to achieve their ambitions for silverware across all competitions once this season resumes.
This season hasn't been straightforward for Cristiano Ronaldo or his teammates, as Simone Inzaghi's Lazio are serious title challengers - unbeaten in the league since late September.
In contrast, Juventus have suffered inconsistent form across all competitions this season, despite their quality and squad depth. They were trailing 1-0 to Ligue 1 side Lyon in their Champions League last-16 clash before the pandemic suspended play.
In addition, they needed a stoppage-time penalty via Cristiano Ronaldo himself to help bail them out of another precarious situation in their Coppa Italia semi-final against Milan.