Umaga finished second at the tournament in Las Vegas earlier this month, going down to the USA's Scott Giller in the final of the men's master 4 brown super heavyweight division after winning his quarter-final and semi-final earlier in the day.
Brown belt is the highest senior belt rank in Brazilian jiu-jitsu under the black belt ranks and requires that fighters be at least 18-years-old to receive it. The IBJJF also recommends fighters have spent a minimum of 18 months as a purple belt - the rank below brown.
Despite Umaga's brown belt event happening on Thursday September 1, Umaga's success wasn't widely known until two weeks later when the International Brazilian Jiu-Jitsu Federation shared a photo of the rugby star to their social media.
In the picture, Umaga is seen wearing a traditional gi [the uniform of a Brazilian jiu-jitsu fighter] with his hand raised in triumph and sporting a massive grin.
"All Blacks rugby legend Tana Umaga having a great time at the World Masters 2022," the IBJJF captioned the picture.
The image quickly went viral with fans and even the Blues, who Umaga re-joined last month as a coaching consultant, congratulating the 49-year-old.
"What can’t he do," the Blues said.
Fellipe Andrew, a black belt who also represents the Alliance gym, also congratulated Umaga with emojis while calling him a "monster".
Current All Black and Blues star Rieko Ioane also like the post.
Umaga has been practicing Brazilian Jiu-Jitsu since 2012, having retired from his 74-Test rugby career in 2011 after a brief return to Super Rugby with the Chiefs.