A by-election was held in the state electoral district of Cootamundra on 14 October 2017. The by-election was triggered by the resignation of Katrina Hodgkinson (). The by-election was won by Steph Cooke for the National Party on preferences. The Nationals suffered a 20% swing on first preference votes and 10% on a two-party basis.
The by-election was held on the same day as by-elections in Blacktown and Murray.
The candidates in ballot paper order are as follows:
<includeonly> Katrina Hodgkinson () resigned.</includeonly>