In February 2000, Arriva North West purchased MTL Trust Holdings, which created a larger presence in the Merseyside area and more than doubled the size of the company.

[4][12][better source needed] In July 2005, Arriva purchased Blue Bus & Coach Services for £2.9 million, which almost doubled their presence in Greater Manchester.

[1][better source needed] During the 2010s, Arriva North West heavily invested in Wright Eclipse Gemini bodied Volvo B5LH hybrid electric double decker buses, operated mainly alongside its fleet of conventional diesel Alexander Dennis Enviro400s.

In 2014, nineteen Caetano EcoCity compressed natural gas-powered buses entered service with the company,[19] followed by a batch of twelve BYD Alexander Dennis Enviro200EV battery electric buses at Green Lane depot in November 2017, which were both the first fully electric powered vehicles operated by Arriva North West and the first Enviro200EVs to be delivered to an operator in the United Kingdom outside London.

[20] Arriva North West took delivery of ten Alexander Dennis Enviro400FCEV fuel cell buses funded by the Liverpool City Region Combined Authority in early 2023, intended for use on service 10A between Liverpool and St Helens via Knowsley in partnership with Stagecoach Merseyside and South Lancashire,[21][22] however issues with the supply of hydrogen fuel have meant that Arriva's Enviro400FCEVs have yet to regularly enter service.