Johnson made her professional boxing debut in 2016 against Napaporn Ruengsuwan winning the fight by second round stoppage. After a successful 2017, Johnson last fight of the year was against Filipino boxer Gretel de Paz for the WBA Oceania Bantamweight title. Johnson won the fight by unanimous decision. A few months later, Johnson fought for the WIBA World bantamweight title against Thailand boxer Rungnapha Kaewkrachang. Johnson won the fight by stoppage. In August 2018, Johnson competed in her tenth professional boxing fight against Thailand boxer Siriphon Chanbuala. Johnson won the fight by second round Knockout. In March 2021, Johnson fought Shannon O'Connell for the WBA Gold World Bantamweight title losing by split decision. In October 2022, Johnson defended her world title against
Susie Ramadan on the
Devin Haney vs. George Kambosos Jr II undercard. Johnson won the fight by unanimous decision, becoming the first Maori World champion boxer to successfully defend a world title. In November 2022, Johnson signed with promoter
Lou DiBella under DiBella Entertainment. On 10 June 2023, in London, England, Johnson lost her title to
Ellie Scotney by unanimous decision. Johnson became a two-time world champion when she defeated the previously unbeaten
WBA female bantamweight World title holder
Nina Hughes at the
RAC Arena in Perth, Australia, on 12 May 2024 by majority decision. The victory was marred by confusion when ring announcer Dan Hennessey initially declared Hughes the winner before correcting himself and announcing Johnson as the victor. In the aftermath, the WBA made Hughes the mandatory challenger for the title and a rematch was scheduled to take place in Sydney, Australia, on 22 March 2025. Johnson won by stoppage in the seventh round. In her sixth consecutive world title fight, Johnson faced
Shurretta Metcalf for the
undisputed female bantamweight title on 11 July 2025, at
Madison Square Garden in New York. She won by stoppage in the ninth round. Johnson was scheduled to make the first defense of her undisputed title against
Amanda Galle at the
Kaseya Center on the undercard of the
Jake Paul vs. Gervonta Davis fight on 14 November 2025. However, the event was cancelled less than two weeks before it was set to take place due Davis' legal issues. The contest was rescheduled to take place at the same venue on 19 December 2025 as part of the undercard of the
Jake Paul vs. Anthony Joshua fight. Johnson won by unanimous decision. ==Media appearances==