He quickly achieved more important roles and appeared as The Prince of Homburg at the Deutsche Theater under the direction of Max Reinhardt.

He landed his breakthrough role as the "dashing" Freder Fredersen in Fritz Lang's epic film Metropolis (1927).

[1] Fröhlich described Lang as a demanding director, recalling that "In scenes of physical discomfort, he tormented his actors until they did suffer".

In 1930, he was called to Hollywood to play roles in German versions of American films such as Die heilige Flamme and Kismet.

During the Third Reich, Gustav Fröhlich remained one of the foremost male stars in German film (along with Hans Albers, Willy Fritsch and Heinz Rühmann).

His best-known role during this time was perhaps in Die Sünderin (1951) with Hildegard Knef, in which Fröhlich portrayed a terminally ill painter.