He was the CEO of Stockholms Enskilda Bank 1946–1958 and during half a century – from the early 1930s until his death in 1982 – he led and reconstructed many of Sweden's largest companies.

During World War II, Marcus, together with Erik Boheman, were appointed to conduct the Swedish trade negotiations.

The historian of business and author Ronald Fagerfjäll [sv] describes him as Europe's most powerful banker of the 20th century.

Wallenberg pursued banking studies and had various jobs in Geneva, London, New York City, Paris, and Berlin from 1920 to 1925.

[8] During the 1950s, he was chairman of the board of AB Atlas Diesel, LM Ericsson, Scandinavian Airlines and the Swedish Bankers' Association.

Wallenberg was a member of the Economic Planning Council (Ekonomiska planeringsrådet) from 1962 to 1964 and chairman of the International Chamber of Commerce from 1965 to 1967.

[11] Wallenberg died on 13 September 1982 in his residence, the Villa Täcka Udden on Djurgården in Stockholm, after having been ill since the beginning of the year.

The bells of the Riddarholmen Church rang the so-called Serafimerringning because Wallenberg was a Knight of the Royal Order of the Seraphim.

He had built a private cemetery on Vidbynäs in Södertörn south of Stockholm, which was Wallenberg's residence until his wife's death in 1978.