He began to study a mechanical engineering in 1902 and he graduated in 1907 at the University of Vienna. He got his doctor's degree in 1911 from the Technical faculty in Vienna. The study of an electrical engineering at Technical faculty began not until 1904, so Vidmar had to take special examinations of the field basics. He was a professor at the University of Ljubljana, a member of the Slovene Academy of Arts and Sciences (SAZU), and the founder of the Faculty of Electrical engineering. Between 1928 and 1929 he was the 10th Chancellor of the University of Ljubljana. In 1948 he established the Institute of Eletrotechnics that now bears his name.

Vidmar was also a top-class chess International Grandmaster, ranking fourth among the world elite, including Lasker, Capablanca, Alekhine, and Euwe, as the only amateur player among professionals.

His successes include victories at some of the top chess tournaments of his time (Carlsbad 1907, Prague 1908, San Sebastian 1911, Budapest 1912, Vienna 1918, London 1922, Hastings 1925, Semmering 1926, New York 1927, London 1927, Bled 1939, Basel 1952). The Slovene Chess Federation organizes an international chess grandmaster tournament named the Milan Vidmar memorial.

Vidmar wrote several books on chess, including Pol stoletja ob šahovnici (Half a century at the chessboard) (Ljubljana 1951), Šah (Chess), Razgovori o šahu z začetnikom (Conversations on chess with a beginner), and, in German, Goldene Schachzeiten (The Golden Times of Chess) and others Transformatorji (Transformers), Problemi prenosa električne energije (Problems of electric energy transmission), Pogovori o elektrotehniki (Talkings about electrotechnics), Med Evropo in Ameriko (Between Europe and America), Moj pogled na svet (My view of the World), Oslovski most (Pons asinorum) (Merkur, Ljubljana 1936).