Hong Kong's population is expected to climb from 7 million to almost 8.9 million people over the next 29 years, the government said in figures released Thursday.
The projections also indicated the proportion of men to women was set to shrink.
The figures from the Census and Statistics Department estimated that from mid-2009 to mid-2039, there will be a natural population increase of 1.05 million people due to births outpacing deaths.
They also forecast an additional increase of 840,000 Hong Kong residents due to net immigration.
As a result, Hong Kong's population was set to age.
"The proportion of the population aged 65 and over is projected to rise markedly, from 13 per cent in 2009 to 28 per cent in 2039," said Fung Hing-wang, the statistics department's commissioner.
The median age of the population was also predicted to climb from 40.7 years in 2009 to 47.6 years in 2039.
The gender ratio was also predicted to shift.
The statistics show that there were 889 men for every 1,000 women in 2009, a number projected to fall to 744 in 2039.
But between the ages of 25 and 44, women were set to outnumber men by the same date, due to the influx of mainly female foreign domestic workers.