Her breakthrough came in 1959 when she was a hostess on
Lennart Hyland's television show . The same year, she won
Melodifestivalen with the song "Augustin", but did not get to represent Sweden in
Eurovision Song Contest, as
Brita Borg was internally selected to sing the song in
Cannes. With the song "Augustin", Malmkvist got her first hit song. It went on to place fourth on
Show-Business magazine's bestseller list on 1 March 1959, and sold over 60,000 copies. One year later, Malmkvist would represen Sweden in the
Eurovision Song Contest 1960 in
London with the song "
Alla andra får varann", where she ended up placing tenth. In the Swedish Melodifestivalen the same year,
Inger Berggren and
Östen Warnerbring had won with the same song song, but Malmkvist had been internally selected for Eurovision. Malmkvist again won
Melodifestivalen in 1961, with the song "April, April", but again,
SVT internally selected another singer to perform it in Eurovision, this time
Lill-Babs. In 1959, she launched her career in West Germany, where she became very popular. In 1960, she released the song "
Die Liebe ist ein seltsames Spiel" under the pseudonym "Die Jolly Sisters". Later, she would release the song in Sweden as well with the title "", which became a hit, topping the chart for seven weeks and selling over 97,000 copies. Her next song, "", sold over 80,000 copies. Along with
Umberto Marcato, she sang the song "" in Italian and peaked at number 58 for five weeks. 1968 Malmkvist had success in the singing competition Schlager-Festspiele in
Baden-Baden. At the debut in 1962, she placed second with "". In 1968, she won the competition once again with the song "". In 1969, she won the West German selection for the
Eurovision Song Contest the same year with the song "
Primaballerina", placing seventh in
Madrid. To this day, Malmkvist's songs remain popular in Germany. In
Melodifestivalen 1988, she participated with the song "". She soon also showed talent on stage; she had the leading role in the musical
Irma la douce. She also participated in the at
Folkan in 1972, and in the
Karl Gerhard show at
Vasateatern. In 2008, she played Fräulein Schneide in
Colin Nutley's version of the musical
Cabaret at
Stockholms stadsteater. In later years she has done many shows, including on
Hamburger Börs in Stockholm, along with
Lill-Babs and
Wenche Myhre. She participated in
Melodifestivalen 2004 with the song "
C'est la vie" along with
Towa Carson and
Ann-Louise Hanson. The trio went on to sing at
Allsång på Skansen, which is broadcast on SVT. Between 2003 and 2012, Malmkvist participated in the Arlövs revue show every year. In 2003 and 2004, she took part in the
Diggiloo summer tour. On 2 June 2004, Malmkvist, along with
Wenche Myhre and
Gitte Henning, debuted their show , in Germany,
Austria and
Switzerland. The tour continued until June 2008 in
Kiel, with a total of 350 shows. Together with actor
Thorsten Flinck, she recorded a Swedish cover of
Nick Cave/
Kylie Minogue's 1995 hit "
Where the Wild Roses Grow", called "". In 2005, Malmkvist participated in the
TV4 show
Körslaget, where she was eliminated first on 5 April. In 2009, she was a celebrity guest on
SVT1's
Stjärnorna på slottet, where she discussed her life and career. Between 2010 and 2011, Malmkvist, along with
Lill-Babs and
Ann-Louise Hanson, had a show called . In 2010, Malmkvist published her memoirs, named . In 2011, she performed at
Allsång på Skansen performing a medley of her hits. In 2012, she participated on the SVT show , the Swedish version of
Who Do You Think You Are?. On the show, she was told her ancestors were soldiers at the
Battle at Poltava and that she had
Snapphanar amongst her relatives. Malmkvist signed on to be a celebrity dancer on ''
Let's Dance 2020'', which is broadcast on
TV4. However, on 17 March it was revealed that she would not participate because of
restrictions concerning the COVID-19 virus. In 2021, she took part in two episodes of the TV4 show
Så mycket bättre. In 2023, Malmkvist was a guest celebrity judge on the episode "MARATHON Talent Hunt" of the Swedish-language reality television series
Drag Race Sverige broadcast on
SVT1 and
SVT Play. In 2025, the documentary film () premiered in Swedish cinemas. In December of that year, SVT broadcast a three-part documentary series on Malmkvist's life and career, called
Siw. On 24 December 2025, Malmkvist was the (), the presenter for SVT's Christmas Eve broadcasts. ==Personal life==