[6] Following a fourth–round technical knockout of Anwar Alfadi on 21 March 2013, Butler challenged Yaqub Kareem for the Commonwealth super-flyweight title on 20 April 2013, at the Wembley Arena in London, England.

[10] Butler was scheduled to challenge the reigning IBF bantamweight champion Stuart Hall, in the latter's second title defense.

He dominated the fight from start to finish, and won by unanimous decision, with all three judges awarding him every single round of the bout.

[13] Following his victory against Garnica, Butler relinquished the IBF bantamweight title, in order to compete against fighters with whom he had size parity, stating "...I'm a natural 115 pounder".

[16] After suffering the first loss of his professional career, Butler jumped up in weight to super-bantamweight, in order to face Gustavo Molina on 11 July 2015.

[17] After successfully bouncing back from his loss to Tete, Butler returned to super-flyweight to face Hector Rolando Gusman on 3 October 2015.

[25] Butler was scheduled face the undefeated Emmanuel Rodríguez for the vacant IBF bantamweight title on 5 May 2018, at The O2 Arena, on the undercard of the Tony Bellew and David Haye cruiserweight rematch.

[30] Butler notched his first bantamweight stoppage victory in two years on 18 May 2019, knocking Salvador Hernandez Sanchez out in the sixth-round.

[33] Butler was expected to face Joseph Agbeko for the vacant WBO International bantamweight title on 25 June 2021.

[35] Butler was booked to fight Jonas Sultan on 22 April 2022, at the M&S Bank Arena in Liverpool, England for the vacant WBO interim bantamweight title.

Butler was originally scheduled to challenge WBO bantamweight champion John Riel Casimero on 11 December 2021 and 22 April 2022, before Casimero withdrew before the weigh-ins due to gastritis, and not being permitted by British Boxing Board of Control (BBBofC) due to medical guidelines violation, respectively.

[38] Butler captured the vacant title by unanimous decision, with scores of 116–112, 117–111 and 117–111, utilizing out-fighting tactics to control the fight for the majority of the bout.

[40] On 25 August 2022, it was announced that Butler would face undefeated WBA (Super), WBC, IBF, and The Ring bantamweight champion Naoya Inoue in a title unification bout.

It took place on 13 December 2022, at the Ariake Arena in Tokyo, Japan, and was broadcast by Amazon Prime domestically and by ESPN+ in the United States.