Left destitute, his mother pawned her wedding ring to pay for an advertisement looking for work, and eventually became a cook.
He started writing for Arthur Griffith's United Irishman and the Shan van Vocht, a periodical established by Alice Milligan and Ethna Carbery.
O'Hegarty became the IRB representative for Southeast England and joined the Gaelic League and Sinn Féin, and became a strong advocate of the Irish language.
[3] In 1905, he was elected secretary of the local Dungannon Club, which drew in as members Robert Lynd, Herbert Hughes and George Cavan.
It was in this publication that he famously wrote, concerning the visit of King George V to Ireland in 1911: "Damn your concessions, England: we want our country!
O'Hegarty felt that the Abbey Theatre was "doing good for Ireland" and supported W. B. Yeats against attacks from Arthur Griffith and like-minded Nationalists.
His son, Seán Ó hÉigeartaigh, was a founder of the Irish-language publishing house Sáirséal agus Dill.