In 1916, Michael returned to Dublin to take part in the planned insurrection. He received a Volunteer's uniform and as Captain Michael Collins he was second in command to Joseph Mary Plunkett in the General Post Office during Easter Week. Collins made no secret that he admired the realism of men like Sean Mac Diarmada more than the aesthetic Padraig Pearse. And though he played a minor part in the Rising, his sense of duty and clear-headedness were remembered.

Following the Rising, Michael, as a prisoner of war, was sent to Richmond Barracks, Dublin and later to Frongoch internment camp in Wales. He returned home to Ireland in December 1916. But it was at Frongoch where Michael Collins' ability as an organizer became recognized. And immediately following his release, he rebuilt the IRB.