Kenny was just 21 years of age when he was selected as the Home Rule League candidate for a by-election for Ennis in November 1882. Ennis's Home Rule MP Lysaght Finigan had resigned his seat on 15 September 1882, owing to ill-health. According to Kieran Sheedy's The Clare Elections, According to Hugh Weir's Houses of Clare, Kenny was the youngest Member of Parliament at the time. The Redistribution of Seats Act 1885 abolished Ennis's separate parliamentary representation, with effect from the 1885 general election. The former two-seat Clare county constituency was divided for parliamentary purposes was split into the new single-member constituencies of East Clare and West Clare with one member to be elected in each division. Kenny did contest either of the new Clare seats, standing instead in Mid Tyrone, where he was elected. However he continued to interest himself in political developments in Clare. Kenny held the Mid-Tyrone seat from 1885–95. When the Irish Parliamentary Party split in 1890, he opposed Parnell. Indeed, he suffered a black eye at the hands of a Parnellite member Pierce Mahony. Kenny retired from political life in 1895 and apart from his activities as a breeder of pedigree horses, cattle and sheep devoted himself to the practice of law. In 1887, he married Elizabeth Robertson Stewart, daughter of W. R. Stewart, of Lairsill or Lairdshill, Aberdeenshire. They had two sons and two daughters. He was appointed Senior Crown Prosecutor for County Kerry in 1916, and was appointed circuit court judge for Cork City and County in 1925, retiring in 1933. Maurice Healy notes that his term of office had been extended due to the universal respect in which he was held. The Irish Times of 6 October 1941 published Matthew Kenny's memories of Charles Stewart Parnell to mark the 50th anniversary of the latter's death. Matthew Kenny, initially a Parnellite M.P., was a cousin of William Kenny, a Liberal Unionist M.P. The two cousins' tenures on opposite sides in the House of Commons overlapped between 1892 and 1895. Both were descended from Mathias Kenny of Treanmanagh, Kilmurry Ibricken and Dysert, Dysert, Co. Clare. Maurice Healy in his memoirs describes Matthew Kenny with great affection as a judge of exceptional dignity and integrity who was universally liked and respected; his fault, if it was a fault, was the severity of his sentences in criminal cases.
