Inter-county Sloan first played for Down as a member of the minor team in 1966. He won an
Ulster medal that year following a 1–12 to 1–9 defeat of reigning
All-Ireland champions
Derry. On 25 September 1966, Down faced
Mayo in the All-Ireland final. A goal by
J. J. Timoney after 21 minutes gave Mayo a boost and they eventually secured a 1–12 to 1–8 defeat of Down. On 11 June 1967, Sloan made his senior championship début in a 3–9 to 1-10 Ulster quarter-final defeat of
Derry. Sloan enjoyed his first senior success in 1968. A 2–14 to 2–11 defeat of
Kildare gave him a
National Football League medal. Later that year, he won his first
Ulster medal as Down defeated reigning champions
Cavan by 0–16 to 1–8. On 22 September 1968, Down faced
Kerry in the All-Ireland final.
Seán O'Neill got the inside of his boot to a rebounding ball for a Down goal after just 6 minutes.
John Murphy struck for another following confusion in the Kerry goalmouth.
Brendan Lynch's goal from a close-in free in the 59th minute came too late as Down secured a 2–12 to 1–13 victory and an
All-Ireland medal for Sloan. In 1971 Sloan won a second Ulster medal following a 4–15 to 4–11 defeat of Derry. Sloan added a
Dr McKenna Cup medal to his collection in 1972 following a 2–13 to 1–6 defeat of Derry. After losing three successive Ulster finals between 1973 and 1975, Down experienced a resurgence in 1978 as Sloan was in the twilight of his career. A 2–19 to 2–12 defeat of Cavan gave him a third and final Ulster medal. He retired from inter-county football shortly after this victory. ==Honours==