During the past several seasons Denis Parshin has been playing for HC CSKA Moscow in the KHL. Internationally, he was a member of the U18 and then U20 Russian National team. The young forward has also been a member of Russia's senior national team during EuroTour competition that largely takes place between the four European hockey nations. Parshin was drafted by the Colorado Avalanche in the third round 72nd overall in the 2004 NHL Entry Draft. On June 1, 2011, Parshin signed a three-year contract extension to remain with CSKA. During his tenth season with CSKA in 2012–13, after scoring 2 points in 9 games, Parshin was traded to fellow KHL club Salavat Yulaev Ufa in exchange for Igor Grigorenko on October 10, 2012. Parshin continued to struggle offensively with Salavat to post 5 goals in 29 games before ending the season on the injured list. In the off-season, Parshin tenure with Salavat was ended when he was traded, along with Sergei Sentyurin, to Torpedo Nizhny Novgorod in exchange for Dmitri Makarov on May 5, 2013. In May 2014, Parshin signed a three-year deal to play for Siberian side Avangard Omsk, where he became the clubs topscrorer in his first season with a personal record of 25 goals and 56 points. In the final year of his contract with Omsk, Parshin began the 2016–17 season, amongst the club's top two-scoring lines. In 28 games, he contributed with 5 goals and 12 points before he was traded in return to Salavat Yulaev Ufa on November 24, 2016. On the opening day of free agency in the following summer, Parshin returned to another former club, agreeing to a one-year deal with Torpedo Nizhny Novgorod on May 1, 2017. In remaining with Torpedo through the 2018–19 season, Parshin posted his highest offensive totals since 2015, collecting 16 goals and 41 points through 61 games. Having left Torpedo for a second time as a free agent, Parshin agreed to a two-year contract with Metallurg Magnitogorsk on May 1, 2019. In the ensuing 2019–20 season, Parshin notched 10 goals in 49 games with Metallurg before he left nearing completion of the regular season to join his first club outside Russia with HC Košice of the Slovak Extraliga on February 16, 2020.
