On 16 January, at the European Championship Rađen scored in the first game two goals in an 8–5 win against Spain. After next two games without goals, on 21 January in the fourth match, Rađen scored his third goal of the tournament for his national team in a routine victory against Romania 14–5. Nikola Rađen won the 2012 European Championship on 29 January. He scored a goal in the final against Montenegro which his national team won by 9–8.[2] This was his first gold medal at the European Championships.
On 15 May 2015, Serbian media published that Rađen was tested positive for cocaine after the World League game between Serbia and Spain, held on 17 February 2015.[4] The penalty for such doping violation is 4 years of not participating in any kind of sport events. On 18 May 2015, he was officially temporary suspended by FINA due to continued investigation into his positive doping results to cocaine metabolites.[5][6] Furthermore, two days later, Olympiacos, the club with whom he was under the contract, terminated the contract for violating the terms of it.[7] On 24 August 2015, he was officially suspended on a 4-year period by FINA for positive doping results; from tests taking place on 17 February, and nearly two months later, on 15 April.[8]