Born to a Jewish family, Mikhelson began his career as an Engineer after graduating with a degree in Industrial Civil Engineering from the Samara Institute of Civil Engineering in 1977. He started working as a foreman at a construction and assembling company in the Tyumen area of Siberia. One of his initial projects was work on the Urengoi-Chelyabinsk gas pipeline. In 1985, he was appointed as Chief Engineer of Ryazantruboprovodstroy. In 1987, he became General Director of Kuibishevtruboprovodstroy. In 1991, Kuibishevtruboprovodstroy was one of the first companies to undergo privatization after the dissolution of the Soviet Union.