Former world champion Parker tested positive as part of a anti-doping examination carried out the very day of his 11th-round defeat versus UK boxer Fabio Wardley.
Fabio Wardley along with Joseph Parker were part of a pulsating bout staged in the UK capital in late October to establish who would become WBO mandatory challenger facing reigning heavyweight king Oleksandr Usyk.
The fighter was previously next in line to challenge Usyk subsequent to compiling a remarkable six consecutive victories, yet placed his mandatory challenger status in jeopardy in the UK and suffered a stoppage in round eleven.
An ordinary examination conducted on the boxer through the anti-doping organization the day of the match showed an adverse result and leaves the 36-year-old with a battle to prove his innocence.
Parker's promotional company released a statement declaring: "Vada informed all relevant parties that Joseph Parker tested positive following a drug screening carried out on the 25th October. While the matter is investigated, no more comments are forthcoming currently."
The New Zealand boxer was crowned world champion back in 2016 prior to he lost the WBO title through a points decision versus Anthony Joshua in Wales in 2018.
Joseph Parker became an active participant across the United Kingdom since then, fighting eight times altogether on UK territory and moving to Dublin for fight camps alongside esteemed mentor Andy Lee over the past few years.
Guided by Lee, the boxer bounced back from his defeat in 2022 versus Joe Joyce to chalk up several successes positioning him front of the queue to face Usyk until he lost against Wardley.
Following the boxer produced a positive test on the day of the Wardley fight, allegedly for cocaine, an investigation about the test outcome has commenced.