By train: Portrush is the terminus of a branch line from Coleraine, which connects to the Belfast–Derry main line. Trains from Belfast to Portrush via Coleraine take about 1h45m. The station is centrally located.
By car: The A26 from Belfast to Ballymoney and then the A29 north brings you to Portrush in about 1h15m (90 km). The drive along the coast from Derry (via the A2 and A29) takes about 55 minutes.
From Belfast City Airport or Belfast International Airport: Car hire is available at both; the coast road via the Giant's Causeway to Portrush from Belfast International is 90 km. Bus connections exist but are slow and require changes at Coleraine.
A hire car is strongly recommended for exploring the Causeway Coast — the key sites are spread along 30 km of coast road and are awkward to reach by public transport.