The play is startlingly nationalistic, in its last pages encouraging young men to sacrifice their lives for the heroine Cathleen ni Houlihan, who represents an independent and separate Irish state.

"[2] The premiere of Cathleen ni Houlihan initially confused Dublin audiences who had expected a comedic play due to the actor Willie Fay's prior association with comedies.

She tells them that many men have died for her and that more must make sacrifices in order to help her regain her fields and banish the strangers who stole them.

Michael is enchanted by Cathleen's words and vows to join the French army, abandoning his parents and his fiancée despite their pleas.

[1] Michael abandons the everyday concerns of dowries, wedding clothes and land purchases in order to follow Cathleen and give up his life for the nationalist cause.

Cannon Harris describes the significance of Maud Gonne's performance as Cathleen ni Houlihan in expressing the play's nationalist themes.

[9] The British invaders have stolen Cathleen Ni Houlihan's land and exiled her, forcing her to wander the roads in search of help.

The French invaders are seen as "necessary catalysts" for the banishment of the British, while Cathleen herself is a disrupting presence when she visits the Gillane family's home and presents them with a past vision of Irish independence which could be achieved in future.