Dovetail connections were applied for connecting column to column, and beam to beam in traditional timber framed buildings. Previous studies were mainly focused on mechanical behaviour of the connection. However, there was a lack of study on the structural behaviour of the connection under different moisture contents. The goal of this study was to analyse the effects of moisture content on swelling behaviour and structural performance of dovetail connection. Different sizes of 120×120, 180×180, 180×240 mm from larix kaempferi and pinus koraiensis were used. Dimensional changes of dovetail connection made from different species showed different trends with an increment of size. The dimensional changes of member of dovetail connection from larix kaempferi were higher than those of dovetail connection made from pinus koraiensis, whereas the dimensional changes of geometric variables of dovetail connection from pinus koraiensis were higher than those of dovetail connection made from larix kaempferi.