Mission Bay had a population of 4,341 at the 2018 New Zealand census, an increase of 150 people (3.6%) since the 2013 census, and an increase of 207 people (5.0%) since the 2006 census. There were 1,677 households. There were 2,016 males and 2,325 females, giving a sex ratio of 0.87 males per female. The median age was 43.3 years, with 612 people (14.1%) aged under 15 years, 801 (18.5%) aged 15 to 29, 2,115 (48.7%) aged 30 to 64, and 819 (18.9%) aged 65 or older.