Jakob Jensen was born in Helgenæs on Djursland where he grew up on the family farm but he later moved to Aarhus where he worked as a mason and later as a politician.

In the 1880s he became involved in the Social Democratic worker's movements in 1883 he helped establish Murernes Fagforening (Mason's Union) and from 1887 he functioned as the president of it.

During Jensen's tenure the elementary schools on Finsensgade, N.J. Fjords Gade, Samsøgade, Læssøesgade and Ingerslevs Boulevard were built and he was the primary driver behind Marselisborg Gymnasium and the location of Aarhus University.

[1][2] Jakob Jensen was a strong opponent of public intoxication and workers spending their salaries in the nightlife instead of their families.

Elias Ølsgaard made a bust of Jakob Jensen which for many years stood in the great hall in the former Danish National Business Archives building on Vester Allé 12.