The first bishop was Æthelwold, who was the king's confessor and became prior of the Augustinian priory at Nostell in Yorkshire.

This only lasted until the reign of Henry III however, when the Augustinians in Carlisle joined the rebels who temporarily handed the city over to Scotland and elected their own bishop.

The seat of the diocese is the Cathedral Church of the Holy and Undivided Trinity in Carlisle.

The diocese originally only covered the northern parts of Cumberland and Westmorland, and expanded to cover almost the entirety of these, as well as the Furness and Cartmel areas of Lancashire, in 1847, from part of the Diocese of Chester, although this did not take effect until 1856.

Until his retirement on 19 July 2014, AEO was provided by John Goddard, Bishop suffragan of Burnley (from neighbouring Blackburn diocese), who was licensed as an honorary assistant bishop of the diocese in order to facilitate his work there.