The primary theme of John Bull’s Other Island is the harmful effects of colonialism. As part of this theme, George Bernard Shaw considers both the personal effects, including the identity of Laurence Doyle and his friendship with Tom Broadbent, and the broader social effects, in this case on Ireland. “John Bull” is a character who represents the United Kingdom, especially England. He was made popular in the early 18th century. Shaw uses this title satirically to indicate the English attitude toward “owning” Ireland. In addition, the theme of friendship is explored.

Doyle’s Anglophile attitudes seem to help him fit into society while he is living in England, and he does not realize he is losing his identity. Irish-ness has become a nostalgic abstraction, and he believes his broadened perspective will benefit his fellow countrymen when he returns home. Broadbent, despite his affection for his friend, takes a condescending attitude toward all Irish people, and Doyle is both surprised and hurt to find himself lumped together with the others. The more Broadbent claims he gives the people, the more he is actually taking. When he finally even takes his friend’s fiancée, Doyle can see his own self-delusion.

John Bull's Other Island is a comedy by George Bernard Shaw. The political satire explores themes such as nationalism and cultural identity. The latter is examined by taking the "national identities" of England and Ireland, and personifying theme through the characters Laurence Doyle, an Irishman; Nora Reilly, who is also Irish; and Tom Broadbent, an Englishman.

The literal marriage between Broadbent and Reilly symbolizes the union, or "marriage," between England and Ireland. The marriage analogy also explores the stereotypes or national identities of both England and Ireland. Likewise, the analogy examines the complex and, at times, tense dynamics between the two countries, which is similar to a real-life marriage.

Another theme of the play is accepting one's cultural roots. This is exemplified by Laurence Doyle, who adopts the English mentality and way of life. He symbolizes the internationalist perspective of many socialist intellectuals during Shaw's day. Doyle believes that it was England that made him a "man," and that Ireland is a place he chose to leave because it is a land of "hopeless dreams."