He (born 1953) received the degree of cand. scient. in chemistry (gas-phase electron diffraction) in 1980 and the degree of dr. philos. (theoretical chemistry) in 1986, both at the University of Oslo. After postdoctoral positions at the Institute for Mathematics and its Applications (IMA), University of Minnesota in 1986–87 and at the Department of Chemistry, Aarhus University in 1987–89, Helgaker became an associate professor (førsteamanuensis) at the Department of Chemsitry, University of Oslo in 1989, where he became a full professor in 1993.