The immigrant experience
Behold the Dreamers follows the Jonga family as they try to adjust to life in America, and also explores how impossible that adjustment is. They experience documentation issues and eventual deportation, live in poverty because Jende cannot find a good job, and struggle with feeling out of place in America both as immigrants and as black people. Eventually they return to Cameroon, symbolizing that the immigrant experience is a difficult one that often ends in sadness.
The trials of marriage
Both the Jongas and the Edwards's experience marriage issues throughout the novel: Jende tries to assert dominance over Neni and control her, while Clark and Cindy experience infidelity. While the Jongas stay together and the Edwards get divorced, both couples reveal the trials that married couples go through, and that even if a couple stays together, that doesn't mean that they are without their problems.
Class contrasts
The Jongas teeter between working class and poverty throughout their time in America, while the Edwards's are incredibly wealthy. These class tensions are a prominent theme throughout Behold the Dreamers as the two families lives intersect. Neni watches the Edwards's wealthy life when she helps them in their summer house and is in awe of that wealth, while Jende spends his time driving the Edwards's throughout the wealthy parts of New York while they struggle to make ends meet. This contrast of socioeconomic classes highlights the inequality present in America, and how the poor take care of the rich's needs while the rich never notice.
Servitude
Both Jende and Neni are employed as domestic help for the Edwards's at different points in the novel, Jende as a chauffeur, Neni as a childcare provider for their younger son, Mighty. The novel highlights the unique place that servants are placed in, where they observe the secrets and intimate lives of the people they take care of, giving them some power over their employers, while their status as employees means that they also inherently lack power in their jobs. As servants, Jende and Neni also spend as much time with the family as family members, but are never part of the family, putting them in an odd place between family and not family.