He published journalism under the by-lines 'Art' and 'Irish Reader' in several nationalist newspapers, including Sinn Féin and the Irish Volunteer.

In 1903 he became involved in Maud Gonne and Arthur Griffith's campaign against the visit of King Edward VII to Ireland.

When in May the situation became desperate O'Hanrahan told his commanding officer MacDonagh they "were inviting destruction of the factory by incendiary shells, and also of the surrounding thickly populated area".

[9] His brother, Henry O'Hanrahan, was sentenced to penal servitude for life for his role in the Easter Rising.

[10] Wexford railway station is named in commemoration of O'Hanrahan, as is the road bridge over the River Barrow at New Ross.