George Sean Warren pleaded guilty at the High Court in Christchurch this morning to the murder of the 43-year-old woman, whose identity remains suppressed.
Two other men, with interim name suppression, have denied obstructing justice. Other suppressions are also in place.
Justice Gerald Nation remanded Warren in custody for sentencing in Greymouth on June 8. It's expected that the summary of facts will be heard then.
The woman was reportedly shot dead at her home in Greymouth on the afternoon of Sunday, October 22.
Police launched a large-scale manhunt and issued pleas for help in finding Warren.
He was found walking near Arahura Marae the next day in a small township about 33km south of Greymouth and arrested.
Police confirmed "a number" of children were at the property when the shooting happened.
