Soon after the wedding, Krzywicka went to Corsica with her lover Walter Hasenclever, a famous German poet and playwright.

Krzywicka's work on spreading the knowledge about sexual education and birth control made her the most famous feminist of pre-war Poland.

Krzywicka and Boy-Żeleński opened a clinic in Warsaw which gave information, free of charge, about planned parenthood.

She was attacked by right-wing activists, who claimed that Krzywicka was "harming the nation", and by liberal writers, such as Jan Lechoń, Maria Dąbrowska and Jarosław Iwaszkiewicz, who objected to the predominance of sexual themes in her works.

During World War II and the occupation of Poland, Krzywicka had to remain in hiding under a false name because she was placed on the Nazi list of people marked for extermination.