He was first elected to Dáil Éireann in the September 1927 general election for the Monaghan constituency and was re-elected at each subsequent general election until his retirement. After Fianna Fáil's victory in the 1932 general election he was appointed Parliamentary Secretary to the Minister for Local Government and Public Health. He retained this junior ministerial rank through the 1930s and into the 1940s. During this time he was effectively the Minister for Health.
In 1944 Ward banned tampons from the Irish market after fears were expressed from religious circles that they could result in female stimulation. In 1946 he was drawing up legislation for a bill that prefigured, and formed much of, Noel Browne's Mother and Child Scheme. This was not implemented by Fianna Fáil and Browne's efforts to do so led to the collapse of the First Inter-Party Government.
That same year he earned controversy for the government. He owned a bacon factory business in Monaghan. After the manager was dismissed the manager's brother, Patrick McCarvill, a former Teachta Dála (TD) for Monaghan, and a close friend of de Valera, sent a list of allegations about Ward to the Taoiseach Éamon de Valera. He set up an inquiry and the Tribunal reported a month later. Ward was cleared of all charges except tax evasion on payments he received from the business. De Valera insisted he resign and he did so a week later. He did not seek re-election in the 1948 general election and retired from politics. He resumed his medical practice and died in 1966.