The Slave Girl by Buchi Emecheta has several themes that readers can find throughout the book. One that should be obvious is that of abandonment. The main character, Ogbanje, is loved and embraced by her family after so many baby girls birthed by her mother died soon after birth. However, she is abandoned by that family, in part because her parents die but more clearly when her brothers decide to sell her into slavery. Throughout the rest of the story, Ogbanje must cope with being abandoned by the family that had once loved and embraced her.

Identity is another theme throughout The Slave Girl. Since Ogbanje is sold into servitude rather than born into it, the way that she defines herself and her self-worth changes. This becomes further complicated when she is given her freedom and returns to the village where she grew up. She must adjust once again and search for a new identity now that she is no longer a slave.

Finally, the role of women is a major theme throughout Emecheta's story. In the setting of the novel—early-twentieth-century Nigeria—the author asserts that women are always controlled by a man in one way or another. In the case of Ogbanje, she is sold by her brothers into slavery, and even after becoming free, she marries, and her actions are controlled by her husband. On page 112, Emecheta writes:

All her life a woman always belonged to some male. At birth you were owned by your people, and when you were sold you belonged to a new master, when you grew up your new master who had paid something for you would control you.