The elderly professor's ordered life spins dangerously out of control when he falls for a nightclub singer. Immanuel Rath (Emil Jannings) finds some of his students ogling photos of cabaret performer Lola Lola (Marlene Dietrich). He visits The Blue Angel, a local nightclub, in an attempt to catch his students there. Seeing Lola perform, he is driven mad with desire, eventually resigning his position at the school to marry his beloved.

The Blue Angel was the film that launched Marlene Dietrich as a famous film star, brought by the director Josef von Sternberg to Hollywood.