Whale bone was used by Māori throughout New Zealand prehistory as an industrial resource for the manufacture of a range of artefacts. However, the selection of bone and the methods used to process it are poorly understood. This paper details the analysis of a southern right whale (Eubalaena australis) bone working floor that was excavated from a fifteenth‐century coastal fishing camp at Kahukura, on the southeast coast of New Zealand. The whale bone working floor assemblage, comprising a large quantity of debitage fragments, was used to reconstruct reduction methods and to determine the products being made at the site. Rib bones were the main element being worked, and were reduced longitudinally using a chipping technique. The intensive bone working assemblage at Kahukura represents the by‐products from primary processing. This stage focused on reducing the bones into workable portions so that they could be easily transported to another location, where they were likely further reduced into artefacts. Copyright © 2015 John Wiley & Sons, Ltd.