Merthyr RFC player Adam Hoskins has been banned for two years after testing positive for cocaine.
The scrum-half tested positive for cocaine metabolite benzoylecgonine on 3 January 2020 following an Indigo Welsh Premiership match against Ebbw Vale.
Hoskins' ban will expire at midnight on 2 January 2022.
UK Anti-Doping (Ukad) revealed earlier in July that three other Welsh rugby players have been handed bans after failing drugs tests.
Stacey Cross, Ukad's deputy director of legal and regulatory affairs, said: "When athletes choose to take recreational drugs, they not only risk breaking the law and endangering their health, but a ban from sport too.
"Athletes need to be aware that if they use cocaine out of competition and later compete in sport, they may face a lengthy ban if the drug is still in their system when tested."