The Orchestra of Welsh National Opera has 55 members and was formed in 1970. Since then it has become internationally recognised as a world-class ensemble by both critics and audiences. Performing 120 performances of nine operas each year in Cardiff and across the UK, the Orchestra of WNO has performed the full traditional operatic repertoire, as well as more contemporary composers such as Janácek and Tippett. For a full list of members of the Orchestra, see below.

In addition to the operatic work on the main stage, the Orchestra gives three concerts as part of the St David's Hall Orchestral Series concerts in Cardiff with symphonic programmes, and also undertakes a concert tour of Wales each winter with up to 14 concerts taking place all over the country.

Concert work has extended to the BBC Proms in 2002, Llangollen International and also the National Eisteddfod and major concert halls throughout England. It is also one of the two resident orchestras for the BBC Cardiff Singer of the World in competition.

In smaller ensembles and as individual players, members of the Orchestra fulfil a wide programme of events including working with children, adults and elderly people through WNO's work with schools and community groups through WNO MAX.