The A4 the re-appears at the end of the M1 motorway at Junction 15 south of Moygashel, from which point it continues uninterrupted to the border village of Belcoo in western County Fermanagh.

Until 1980, all traffic following the A4 had to leave the M1 at its final junction and travel through Dungannon town centre to rejoin the A4, but a by-pass opened that year continued the A4 route ahead past the final junction of the M1, including a short section of dual-carriageway which had been built at the same time as the construction of the M1 itself.

In wider sections of the road, the hard shoulder has been converted for use as a "slow lane" for a short distance for westbound traffic in two places; between Dungannon and Ballygawley at the Cappagh crossroads, and between Fivemiletown and Brookeborough.

West of Enniskillen town, the A4 passes through the hamlet of Letterbreen and the village of Belcoo, where it then reaches the border with the Republic of Ireland (at a bridge over Lough MacNean into Blacklion) and continues westward toward Sligo as the N16.

The route from Dungannon to Ballygawley (approximately 12+1⁄2 miles; 20.1 km) was upgraded to a dual carriageway standard, with the new road opened in November 2010.

The scheme includes a central reservation safety barrier, a hard shoulder and six grade separated junctions.

The Department for Regional Development plans some future road schemes for the A4: There are a number of tourist attractions on or close to the A4.