She later worked as a television host and as a physician. Between 1950 and 1971, Koch appeared in more than 65 films. In the haunting 1954 espionage thriller Night People she starred alongside Gregory Peck.
In 1971, she resumed the medical studies she had broken off in the early 1950s to become an actress.
She got her Doctor of Medicine in 1974 and practiced medicine until 1997 as a specialist in Munich. She also hosted other television shows and, as of 2014, still has a medical advice program on radio.
Marianne Koch has been in a relationship with the publicist Peter Hamm since the mid-1980s.