MacCurtain is born at Ballyknockane in the Parish of Mourne Abbey on March 20, 1884. He attends Burnfort National School until the family moves to Blackpool on the north side of Cork city in 1897, where he attends The North Monastery School. He becomes active in numerous cultural and political movements and joins the Blackpool branch of the Gaelic League, becoming its secretary in 1902. He works in his early career as a clerk and in his free time teaches the Irish language. He joins the Fianna Éireann in 1911 and is a founding member of the Irish Volunteers.
At the outset of the Easter Rising in April 1916, MacCurtain commands a force of up to 1,000 men of the Irish Volunteers who assemble at various locations around County Cork. MacCurtain and his officers await orders from the volunteer leadership in Dublin but conflicting instructions and confusion prevail and the Cork volunteers never entered the fray. A tense week-long stand-off develops when British forces surround the volunteer hall. A negotiated agreement leads to the surrender of the volunteers’ arms to then Lord Mayor of Cork Thomas Butterfield on the understanding that they will be returned. The weapons are not returned and MacCurtain is jailed in the Frongoch Prisoner of War camp in Wales. Eighteen months later, after the general amnesty of participants in the Rising, MacCurtain returns to active duty as a Commandant of what is now the Irish Republican Army (IRA).
By 1918, MacCurtain is a brigade commander in the IRA. During the Conscription Crisis in the autumn 1918, he actively encourages the hiring of the women of Cumann na mBan to cater for Volunteers. MacCurtain is personally involved with Michael Collins‘ Squad that attempts to assassinate Lord John French, whose car is missed as the convoy passes through the ambush positions. Despite the setback he remains brigadier of No.1 Cork when he is elected the Sinn Féin councillor for NW Ward No. 3 of Cork in the January 1920 council elections and is chosen by his fellow councillors to be the Lord Mayor. He begins a process of political reform within the city.
On his 36th birthday, March 20, 1920, MacCurtain is shot dead in front of his wife and son by a group of men with blackened faces in retaliation for the shooting of a policeman. MacCurtain’s house in the city’s Blackpool area is also ransacked. The assassins are found to be members of the Royal Irish Constabulary (RIC) by the official inquest into the event.
The killing causes widespread public outrage. The coroner’s inquest passes a verdict of wilful murder against British Prime Minister Lloyd George and against certain members of the RIC. Michael Collins later orders his personal assassination squad to hunt down and kill the police officers involved in the attack. RIC District Inspector Oswald Swanzy, who had ordered the attack, is fatally shot with MacCurtain’s own revolver while leaving a Protestant church in Lisburn, County Antrim on August 22, 1920, sparking a “pogrom” against the Catholic residents of the town. MacCurtain is buried in St. Finbarr’s Cemetery, Cork.