She used to sing for All India Radio; she was not allowed to sing playback (even for herself) in the movies with the lone exception being 1972's "Lalkar". In the 1950s, she had string of hits opposite Pradeep Kumar such as "Fashion" (1957), "Detective" (1958) and "Duniya Na Mane" (1959). The films she did with Pradeep Kumar were men-oriented. In 1957, noted Bollywood actor and director Guru Dutt cast Mala Sinha in his film "Pyaasa" (1957) in a role originally intended for Madhubala. Mala Sinha performed in the relatively unsympathetic part of an ambitious woman who chooses to marry a rich man (played by actor Rehman) and have a loveless marriage, rather than a poor, unsuccessful poet; her impoverished lover (played by Guru Dutt) whom she ditches. "Pyaasa" remains to this day a classic in the history of Indian cinema and a turning point for Sinha.