The route has strategic importance, as it connects Downpatrick, Newcastle and Castlewellan with Newry, and thus provides a link with Dublin. Between Castlewellan and Newry, the route passes through rural villages such as Kilcoo and Rathfriland, which would be considered part of the Mourne Country, due to their proximity to the mountains of the same name. Both Castlewellan Forest Park and Tollymore Forest Park are located nearby, as is the afore mentioned seaside resort of Newcastle. The route also passes through the Lecale district.
The A25 travels through Newry in the Rathfriland Road, Monaghan Street and Camlough Road, passing through the heart of the city, and northwestwards towards the city's railway station (located on the Dublin-Belfast mainline). The railway bridge over the A25 is known as the Egyptian Arch and was featured on a Royal Mint coin issued in 2006.[1] The Newry bypass (A1) also bridges above the Camlough Road. The junction between the two routes is currently being upgraded to have motorway characteristics as part of Newry's new bypass scheme (from Cloghoge Roundabout to the Belfast Road).