Bergman was appointed associate professor of mathematics at the University of Uppsala in 1761, and six years later he became professor of chemistry there. His early studies were on rainbows and on the Aurora Borealis, which he estimated to have a height of 740 kilometres (460 miles). Bergman also investigated the pyroelectric properties of the mineral tourmaline and discovered that when a tourmaline crystal is heated, the ends become oppositely charged.

Bergman's most important paper is probably his Disquisitio de Attractionibus Electivis (1775; A Dissertation on Elective Attractions), in which he included tables listing the elements in the order of their affinity (their ability to react and displace other elements in a compound). These tables were widely acclaimed and were included in chemical literature as late as 1808.

Bergman introduced many new reagents and devised analytical methods for chemical analysis. His De Analysi Aquarum (1778; “On Water Analysis”) is the first comprehensive account of the analysis of mineral waters.