Gianina Ernst was born in Winterthur, Switzerland to a German-Swiss family. Her father, Joachim Ernst, was a ski jumper and German champion who, during FIS Nordic World Ski Championships 1982 in Oslo, finished 11th on the K70 hill and 38th on the K90 hill. Her mother, Cornelia Thomas, was a Swiss cross country skier, who represented Switzerland at the 1980 Winter Olympics and 1982 World Championship.