On 8 February 1872 Nolan was elected MP for County Galway in a by-election, defeating by a large majority the Conservative William Le Poer Trench.
The local Catholic bishops and clergy had strongly supported Nolan, chiefly because the family of his opponent, a Captain Trench, was active in proselytism.
When the Irish Parliamentary Party split over Charles Stewart Parnell's long-term family relationship with Katharine O'Shea, the separated wife of a fellow MP, Nolan sided with his deposed leader and seconded the motion to retain Parnell as chairman at the ill-fated party meeting in Committee Room 15 of the House of Commons.
He lost the Galway North seat to an Anti-Parnellite, Denis Kilbride, in 1895 and stood unsuccessfully as a Parnellite for Louth South in 1896.
But at the National Convention of 8 January 1902 he was expelled from the United Irish League on the ground of his 'harsh and unparalleled oppression of his Mweenish tenantry'.