The 36-year-old batter, who represented Northamptonshire Steelbacks, returned an adverse analytical finding for benzoylecgonine, a metabolite of cocaine, following an anti-doping test conducted on 18 July 2026.
The test took place on Finals Day, when Northamptonshire went on to win the Vitality Blast title.
England's Cricket Regulator announced the disciplinary outcome on Thursday, 5 November, confirming that Lynn had accepted the sanction and completed the suspension.
According to the regulator's findings, Lynn admitted using cocaine between 15 and 16 July. He was provisionally suspended on 31 July while the case was being investigated.
The regulator initially sought a three-month suspension but reduced the penalty to one month after Lynn committed to a substance abuse treatment programme, which he completed on 30 August.
The regulator also accepted that the cocaine use occurred outside competition and was unrelated to sporting performance.
One of the two anti-doping charges against the Australian was subsequently withdrawn because the level detected in his sample was below the threshold required under World Anti-Doping Agency rules.
Lynn's cricket career
Lynn is one of Australia's most recognised T20 specialists and holds the record as the Big Bash League's all-time leading run-scorer.
He has represented Australia in four One-Day Internationals and 18 T20 Internationals, while also playing for numerous franchise teams around the world.
The right-handed batter has featured for Brisbane Heat and Adelaide Strikers in Australia's Big Bash League, as well as several teams in overseas competitions.
His one-month suspension has already been served, meaning he is eligible to return to professional cricket.
Big Bash League future uncertain
Lynn has been linked with a possible move to Melbourne Renegades ahead of the upcoming Big Bash League season, although he has yet to secure a confirmed deal.
Any further disciplinary action beyond the suspension imposed by England's Cricket Regulator would be a matter for his prospective club.
The case has attracted attention because the positive test occurred on the day Northamptonshire celebrated their Vitality Blast title triumph, although the regulator accepted that the substance use was unrelated to sporting performance.