The size of Mullalyup is approximately 82.7 square kilometres. It has 16 parks covering nearly 66.5% of total area. The population of Mullalyup in 2011 was 435 people. By 2016 the population was 149 showing a population decline of 65.7% in the area during that time. The predominant age group in Mullalyup is 50-59 years. Households in Mullalyup are primarily childless couples and are likely to be repaying $1400 - $1799 per month on mortgage repayments. In general, people in Mullalyup work in a managers occupation. In 2011, 84.6% of the homes in Mullalyup were owner-occupied compared with 81.5% in 2016.