Pygmalion's resolution has been a source of controversy since its first performances. Eliza becomes resentful of Higgins's treatment of her, particularly the way he overlooks her contribution to his success with the bet. She is also concerned for her future: she is aware that, due to her background, she can never be fully accepted by the upper class, but her new manners make her unwilling to settle back into her old life. Motivated by an almost existential anguish, Eliza leaves Higgins.

When Higgins confronts her, Eliza shares her intentions to marry Freddy one day. She enrages Higgins further by threatening to become a phonetics teacher herself, so she can teach others what he has taught her, while also earning a living. Ultimately, Eliza realizes her power over Higgins and her own self-worth. The play ends inconclusively, with Eliza leaving for her father's wedding and Higgins believing Eliza will inevitably return to him.

Famously, audiences were not too fond of this resolution. In traditional comedies, the main male and female leads would have ended up together by the last curtain. Crowds were perhaps expecting an ending more in line with Shakespeare's Much Ado About Nothing, where the bickering Beatrice and Benedick fall in love. Later versions of Pygmalion have taken the opposite approach to the play's ending: the 1938 film version and the 1956 musical My Fair Lady (as well as its subsequent 1964 film adaptation) conclude with scenes implying Eliza and Higgins will marry.