The basic unit of the Order is a Council; which may cover a single or number of local church parishes. Councils will meet once or twice monthly.

When Councils are erected; they receive a KSC 'Charter of Constitution', empowering them to conduct meetings under the Order's name; elect members as Office Bearers; initiate new members; create their own rules and bye-laws and entitlement to full representation at Provincial Council meetings.

Each Charter Council is autonomous under the constitution; elects its own executive, with the presiding officer being the Grand Knight. In addition to its various officers, every Council should have a Chaplain, duly approved by the Bishop of the diocese in which the Council is established. There are in excess of 340 KSC Councils in the Order.

Groups of Councils are formed into a Province, which meets quarterly. The Provinces of the Knights have generally corresponded to the areas covered by the Catholic dioceses of the country, although today there tend to be more sub-divisions. Provinces are established by the Board of Directors to co-ordinate the work of a number of subordinate Councils in a given area. A Province is an important branch in the structure of the Order; through it the vast volume of work of the Order is organised and carried out.

Within the framework of the constitution and rules of the Order; a Province has autonomy; conducts its proceedings and supervises the Councils of which it is comprised. It is headed by a Provincial Grand Knight (the office used to be called Provincial Deputy) who, representing the Supreme Knight and Board of Directors in what is usually a very large area, has a position of some importance in the Order.

The Supreme Council is the governing body of the Order of the Knights of St Columba. Members from throughout the KSC meet each September, in changing locations, to discuss the Order's development and future policy. Decisions taken by Supreme Council are final and the Board of Directors are responsible for their implementation. The Supreme Knight, Supreme Officers and Directors are elected annually by the Supreme Council; as the Order's Board of Directors.