Tarczynski also competed in the 100 m backstroke at the 2012 Summer Olympics in London. He cleared both a national record and a FINA A-cut of 54.12 from the Polish Long Course Championships in Olsztyn. He challenged seven other swimmers in heat five, including France's top favorite Camille Lacourt and Russia's Arkady Vyatchanin, bronze medalist in Beijing four years earlier. Tarczysnki saved a seventh spot over Lacourt's teammate Benjamin Stasiulis by three-tenths of a second (0.30), in a time of 55.06. Tarczysnki failed to advance into the semifinals, as he placed twenty-seventh overall on the second day of prelims.