A by-election was held for the New South Wales Legislative Assembly electorate of Patrick's Plains on 8 February 1866 because Bowie Wilson had been appointed Secretary for Lands in the second Martin ministry. Such ministerial by-elections were usually uncontested however on this occasion a poll was required in Patrick's Plains and Yass Plains (Robert Isaacs). Both ministers were comfortably re-elected with more than 70% of the vote. The other ministers James Martin (The Lachlan), Henry Parkes (Kiama), James Byrnes (Parramatta) and Geoffrey Eagar (West Sydney) were re-elected unopposed.