He was the son of Patrick "Patt" Lalor of Tenakill, Mountrath, Queen's County, who had himself been an M.P.
He then won the new Queen's County (Leix) seat in 1885, defeating his Conservative opponent by more than 7 to 1.
T. P. O'Connor described him in 1886: "Today he is a feeble and bent man with wearied eyes and a thin voice, but his spirit is exactly the same as in his hot youth.
In 1848 he had his pike and his thousands of pikemen ready for action; today, as then, he is the unconquerable and irreclaimable rebel – the Blanqui of Irish politics.
His grandson John Lalor Fitzpatrick (1875–1956) was also a nationalist member of the House of Commons for the Ossory division of Queen's County (1916–18).