Kennington had a population of 114 at the 2018 New Zealand census, a decrease of 9 people (−7.3%) since the 2013 census, and unchanged since the 2006 census.
The town of Kennington experienced a decrease in its population from 123 to 114 between the 2013 and 2018 censuses, with no change observed from 2006. The population has been steadily decreasing over this period.