Despite both his wife Dorothea's success as a playwright, and his own increasing popularity as an author, Byrne's financial straits forced his family to sell their house in Riverside, Connecticut, and return to Ireland. They later purchased Coolmain Castle, near Bandon in County Cork, where Byrne lived until his death in a car accident due to defective steering, in June 1928. A Kilbrittain man, Cornelius O'Sullivan, who witnessed the incident pulled him from the water and tried to revive him, but to no avail. He is buried in Rathclarin churchyard, near Coolmain Castle. His headstone reads, in Irish and English: "I am in my sleeping and don't waken me."