Peñíscola sits on the A-7 motorway and N-340 coastal road, both well signed. By car from Valencia it is about 130 km north (roughly 1.5 hours); from Barcelona it is around 230 km south (just under 2.5 hours).
The nearest train station is Benicarló-Peñíscola, about 8 km from town on the Valencia–Barcelona line (Renfe Media Distancia and some long-distance services). From the station, taxis are reliable and inexpensive; there is also a local bus service, though frequency drops outside summer. Journey times: around 1.5 hours from Valencia, 3 hours from Barcelona.
There is no airport at Peñíscola itself. The nearest usable airports are Valencia (150 km south) and Reus (120 km north), both with international connections. Barcelona El Prat is further but has far more routes.
In summer, direct bus services run from Valencia and other cities to Peñíscola town centre. Check with ALSA for timetables.