Mlynár has mainly participated in the Slavic Cup since 2006 . He has had 13 victories so far and won the overall standings in the 2010/11 season . In season 2015/16 he finished second and in season 2017/18 and 2019/20 third in the standings (as of the end of season 2019/20). After participating in two relays in the World Cup, he ran his first World Cup individual race in November 2008 in Kuusamo , which he finished with 47th place in the sprint. At the 2010 Winter Olympics in Vancouver , he finished 57th in the sprint and 12th place in the relay. At the Nordic World Ski Championships in Oslo in 2011 he reached 62nd place in the sprint and 12th place in the team sprint. His first and so far only World Cup points he got at the Tour de Ski 2011/12 with 18th place in the sprint stage race. His best results at the Nordic World Ski Championships 2013 in Val di Fiemme were 38th place in the sprint and 20th place in the team sprint. At the Nordic Opening in Kuusamo at the beginning of the 2013/14 season, he came in 90th. At the 2014 Winter Olympics in Sochi , 51st place over 15 km was classic and 17th place in the team sprint was his best placings. In February 2015, at the 2015 Nordic World Ski Championships in Falun, he achieved 65th place over 15 km freestyle, 41st place in sprint and 22nd place in team sprint. At the 2015 World Cup Mini Tour in Ruka , he finished 61st and the following year in Lillehammer 73rd place. At the beginning of July 2016 he won the Rollerski World Cup in Oroslavje in the 10 km mass start race. At the 2017 Rollerski World Championships in Sollefteå , he and Miroslav Šulek won the bronze medal in the team sprint. His best placings at the 2018 Winter Olympics in Pyeongchang were 23rd place in the sprint and 22nd place together with Andrej Segeč in the team sprint. In January 2019 he won the Biela Stopa over 50 km freestyle and 30 km classic.