The Northern Ireland Ornithologists' Club was formed in 1965.  Its purpose then, as now, was to focus the interests of active and enthusiastic birders.

The club's activities are arranged by a committee, elected at the Annual General Meeting held each January. These activities are mainly fortnightly meetings, which take the form of illustrated talks by club members or guest speakers, held between October and April, and a series of Field Trips, both local and further afield.   The club tries to have at least two of the speakers from outside Northern Ireland. The club also organises an annual photographic competition, open to all Northern Ireland bird photographers.  This culminates in a photographic show, usually in March, at which entries are displayed and winners announced. 

Whilst the objectives of the club are related to ornithology rather than conservation, links are maintained with the RSPB,  Wildfowl & Wetlands Trust and the Ulster Wildlife Trust, and many members are individually affiliated to such groups.

Members are sometimes invited to take part in population studies, on behalf of the British Trust for Ornithology (BTO), for example.  The NIOC is also a member of the "BTO - Bird Clubs Partnership".  From time to time the club also organises its own field surveys and the results are made available to non-members and organisations on request.