[4] Plunkett contracted tuberculosis (TB) at a young age and spent part of his youth in the warmer climates of the Mediterranean and North Africa.

Plunkett's interest in Irish nationalism spread throughout his family, notably to his younger brothers George and John, as well as his father, who allowed his property in Kimmage, south Dublin, to be used as a training camp for young men who wished to escape conscription in Britain during the First World War.

Sometime in 1915, Joseph Plunkett joined the Irish Republican Brotherhood and soon after was sent to Germany to meet with Roger Casement, who was negotiating with the German government on behalf of Ireland.

Casement's role as emissary was self-appointed, and, as he was not a member of the IRB, that organisation's leadership wished to have one of their own contact Germany to negotiate German aid for an uprising the following year.

Casement, on the other hand, spent most of his energies recruiting Irish prisoners of war in Germany to form a brigade to fight instead for Ireland.

[7] During the Easter Rising, Plunkett and Patrick Pearse argued in a conversation with Desmond Fitzgerald that it would be beneficial for Prince Joachim of Prussia to be crowned king.

He had an operation on his neck glands (probably goiter[citation needed]) days before Easter and had to struggle out of bed to take part in what was to follow.

Still bandaged, he took his place in the General Post Office with several other of the rising's leaders such as Patrick Pearse and Tom Clarke, though his health prevented him from being active.

[10] The main railway station in Waterford City is named after him as was Joseph Plunkett Tower in Ballymun which has since been demolished.