Educated at Belvedere College, at the age of sixteen James White joined the John Player tobacco company as a clerk, subsequently rising to the position of assistant manager. In tandem with his professional career and reflecting his deep personal interest in art he developed a parallel career as an art critic. Under the name James White he established himself as a critic, continuing to use his given name Patrick White for his work at John Player & Sons. He was a critic for The Standard, and later for the Irish Press, at the same time, travelling around Ireland giving lectures on Irish art, while he pursued his business career. In 1953 he organised the Congress of International Art Critics in Dublin and he was one of the first commentators on Irish Art to recognise the talents of Louis le Brocquy who came to prominence in the 1940's. In addition to his work as a critic he lectured in art history at University College Dublin and Trinity College Dublin.
As well as writing and lecturing, throughout the 1950s White organised numerous exhibitions with a view to exciting public interest in art. In 1960 he switched careers to become Curator of the Dublin Municipal Gallery where he had the opportunity to combine his business acumen with his deep interest in art, most notably to promote the institution among the general public. His successful stewardship of the Municipal was noticed and on 1st June 1964 he was appointed Director of the National Gallery of Ireland, his term a position he retained until 1980. His term of office was notable for the acquisitions made with the support of the Shaw Fund and the exceptional growth in visitor numbers achieved during his tenure. He also served on the Arts Council in the 1960s with Michael Scott for many years.