CairnryanベースのP&O European Feries (Felixstowe)のLtd.とPandoro社の合併により1998年に設立、本社は英国のDoverにおかれた。1999年、三菱重工建造のRo/Roカーフェリー、European Causeway (2000), European Ambassador (2000), European Highlander (2002)をLiverpool - Dublin航路に投入。2010年、P&O Ferries社に併合。

P&O Irish Sea was formed in 1998, following the merger of the Cairnryan-based service of P&O European Ferries (Felixstowe) Ltd and Pandoro (who operated routes between England, Scotland and France to Ireland).[1] The following year (1999), the new P&O Irish Sea announced its intentions to purchase a purpose-built Ro-Pax (roll-on, roll-off, vehicle/passenger) vessel from Mitsubishi of Japan for the Liverpool to Dublin route. This would see the transfer of the European Leader to the Fleetwood route.

In 2004, P&O closed its Fleetwood – Larne services with the sale of all interests. In addition to the service rights, European Leader, European Pioneer and European Seafarer were sold to the Swedish Stena Line group. At the same time, P&O announced the closure of the Mostyn – Dublin service due to low passenger numbers. This led to the sale of European Ambassador and European Envoy for further service in Europe.[citation needed]

In 2010, P&O Irish Sea was merged back to being its parent company again.