Her career as a performer of musical theatre began with small-scale concert presentations of Chess, in which she sang the role of Florence. She took part in a number of smaller productions, including Little Dorrit in Enskede and the musical Elvira Madigan at Malmö Music Theatre in Malmö, Sweden.
Her big breakthrough occurred when she created the title role in Benny Andersson and Björn Ulvaeus' Kristina från Duvemåla, a role she played on and off for nearly four years (during the musical's entire run). In 1998, she played Hodel in Fiddler on the Roof, taking a break from Kristina. In 2000, she returned to Malmö Music Theatre to portray the role of Fantine in Les Misérables, and in 2002 she created the role of Florence in the reconceived Swedish production of Chess, opposite original London star Tommy Körberg as Anatoly. Having left this production upon closing in 2003, Sjöholm took part in Chinarevyn, a revue starring many well-known Swedish performers including Magnus Härenstam, Lasse Berghagen, Loa Falkman, Sissela Kyhle and herself.
Helen Sjöholm has also toured extensively throughout Sweden with Jojje Wadenius and Martin Östergren and she has released two albums, Visor (2002) (a collection of more or less well-known Swedish folk songs in new arrangements by Östergren) and Genom varje andetag (2003) (featuring music and lyrics by jazz pianist Anders Widmark).
She is also a frequent performer with Benny Andersson's band, Benny Anderssons Orkester (BAO), singing mostly dance music and music by Andersson. Additionally, she has appeared in numerous gala concerts including Rhapsody in Rock.
She first appeared on the big screen in 1999, appearing in Rikard Hobert's Där regnbågen slutar. In 2004, she returned to the movies, portraying the role of Gabriella in Kay Pollak's much-debated Så som i himmelen (As It Is in Heaven).
Hit recordings include Du måste finnas (from musical Kristina från Duvemåla), Vår sista dans (with Benny Anderssons Orkester), Gabriellas sång (from film Så som i himmelen aka As It Is In Heaven), Jag vet vad han vill (aka I Know Him So Well from musical Chess), Det är vi ändå (with Tommy Körberg and Benny Anderssons Orkester) and Du är min man (with Benny Anderssons Orkester), a.o.