Monroe made his debut on March 27, 2008 against Erix Quinteros. After winning his first 10 fights, his first lost came against Darnell Boone in 2011. After the loss he was released by his promoter.[2] After 17 months without a fight, Monroe returned to the ring in August 2012.[3] In 2014 he won the Boxcino Tournament which aired on ESPN 2.[4]

In January of 2015 he went on to defeat Bryan Vera, a fighter many expected Willie would lose to. Once again he proved the critics wrong by earning the unanimous decision over Vera and solidifying his position amongst the elite at the middleweight division. Less than 4 months after that fight he fought Gennady Golovkin for the middleweight championship of the world in a nationally televised fight on HBO

Willie won his comeback fight on June 11th, 2016 when he faced 2015 Boxcino middleweight champion, John Thompson (17-3, 6 Kos). He returned from a 13 month layoff and dropped Thompson twice en route to a unanimous decision and his 20th victory.

Monroe most recently was back in the ring on September 17th, 2016 at AT&T Stadium, home of the Dallas Cowboys, in Arlington, Texas as the co-main event for the Saul “Canelo” Alvarez vs. Liam Smith championship bout. This time he fought Gabriel Rosado (23-9, 13 Kos) who appeared in the movie “Creed”. This bout was televised live on HBOPPV to millions around the world, who saw Monroe defeat Rosado.

Brick X Brick Willie "El Mongoose" Monroe JR. from Will Strawser on Vimeo.