Dmitry Mazepin was born on April 18, 1968 in Minsk, graduating from the Suvorov Military Academy in Minsk in 1985. After this, he was educated as a military interpreter. Dmitry Mazepin did his military Service in Afghanistan in 1986—1988 as an interpreter. He graduated from the MGIMO University's Department of Economics in 1992 before going to work in the financial sector of Russia and Belarus and ultimately taking executive positions at major Russian private and government-owned companies. He has been chairman at Uralchem since 2007. He graduated from the Saint Petersburg Institute for Economics and Management in 2008 with a first-tier university degree in Organization Management. He earned his PhD from the same school in 2012 after defending a thesis on developing a methodical approach to managing the stock market potential of an oil producing company.

In the mid-2000s, Dmitry Mazepin became embroiled in a conflict around Gazprom assets. The assets were divested by Nikolay Gornovsky, CEO of Gazprom subsidiary Mezhregiongaz, in late 2002, without permission or knowledge of Gazprom management. Part of these assets ended up in Mazepin’s possession some time after that. Gazprom was able to recover the assets, including an 18% equity stake in Azot Chemicals Company, in 2006.

When Mazepin was an executive officer at the Russian Government Property Fund and Kuzbassugol Coal Company in 2001-2002, Russian Steel, a minority shareholder in Kuzbassugol, accused him of promoting and serving the interests of Severstal and MMK, the Kuzbassugol majority shareholders. As a government official at the Russian Government Property Fund, he also advocated cancellation of a controversial auction to privatize the Eastern Oil Company which went against the best interests of TNK, a private company.

After leaving Sibur, Mazepin decided to go into the chemicals Business for himself. In 2004, Constructive Bureau, a company controlled by Mazepin, acquired a control equity stake in Kirovo-Chepetsk Chemicals Plant. Mazepin claimed originally that he was acting on behalf of Gazprom, but ended up as the beneficiary owner of the chemicals company. Most of the core assets of Mazepin’s Business were spun-off from Gazprom, according to some media.

Starting from 2005, he has been regularly accused of attempting to use illicit (“raider's”) methods to take over Togliattiazot (TOAZ), a public company where he has been consistently persecuting the executives. TOAZ CEO Sergey Makhlai accused Mazepin of making personal threats against himself. According to Makhlai, Mazepin threatened him with instigating a Criminal investigation against him unless he agreed to Mazepin’s terms for selling TOAZ to Mazepin.

In June 2008, Mazepin acquired a 75.01% stake in Voskresensk Mineral Fertilizers, increasing thee stake to 100% in 2011. In the same year, he combined the production facilities of Kirov-Chepetsk Plant and Perm Halogen into Halopolymer, a public joint-stock company. He resigned from the Board of Directors of Halopolymer in 2015.

Forbes magazine placed Mazepin on the list of Russia's 100 wealthiest businessmen in 2010, estimating his personal fortune at US$950 mn. His fortune was estimated at US$1.4 bn as of 2014.

Dmitiry Mazepin joined resources with Mikhail Prokhorov to buy out a stake in Uralkali from Suleiman Kerimov in December 2013, becoming the owner of a 19.99% equity stake. Mazepin took operating control over the company at that time, winning a seat on Uralkali Board of Directors in March.

In May 2014, Mazepin resigned as a regional legislator at the Kirov Regional Duma. Some media link this to allegations leveled against Mazepin for his alleged involvement in making a falsehood-laden political video commercial targeting his political opponents, which has been aired on REN TV, a nationwide Russian TV channel.

Uralkali made a buyback offer for 11.89% of its stock in May 2015. British Business observer and law professor Andrew Ashworth believes that the Uralkali management are trying to drive the stock price down to enable Mazepin to buy a controlling stake and squeeze out minority shareholders. Ashworth notes that Mazepin supports minority shareholders in the Togliattiazot conflict, while disregarding minority shareholders’ rights at Uralkali. Ashworth believes that Mazepin’s actions at Uralkali may constitute unfair stock price manipulation, illegal under the British law. Uralkali minority shareholders include several major international institutional Investors.

He was appointed President and CEO of Sibur, a Gazprom subsidiary, mere months after the previous CEO of the company Jacob Goldovsky was arrested. Mazepin's brief from Gazprom management was to return Sibur under the gas giant’s operating control. After a little over six months as Sibur CEO, Mazepin was dismissed in February 2003.