Cai is one of many Chinese expats who came to Canberra as the parents of students and young workers in the capital's public service over the past two decades.

While Cai and her mahjong competitors largely speak Cantonese, census data released on Tuesday shows Mandarin is now the fastest growing language other than English spoken in the city's homes - largely due to international university students.

The data shows the number of Canberra residents speaking Mandarin at home grew 85 per cent in five years, up from only 1.9 per cent of the ACT population in 2011 - or 6676 people - to 3.1 per cent, or 12,408 on census night last August.

That compares to 4216 Vietnamese speakers, 3853 Cantonese speakers, 3646 Hindi speakers and 3273 Spanish speakers in the nation's capital.

While the ACT remains largely English-speaking, at 72.7 per cent of the total population, the number of households where a language other than English was spoken grew slightly from 21.1 per cent in 2011 to 23.8 per cent in 2016.

The ACT CAA's Jane Toh said the change was partly due to growing numbers of Mandarin speakers from southern China, such as Beijing and Shanghai coming to Australia, rather than those with northern Cantonese dialects.

But she said it was also due to growing use of Mandarin among young Chinese.

Ms Toh said many of those young Chinese came to the capital as international students, often staying on and later bringing their parents to Australia under family reunion visas, after they secured work post-study.

The data also showed more China and Indian-born residents called Canberra home in August 2016, reaching 2.9 and 2.6 per cent of the ACT's total population, compared to 1.8 and 1.6 per cent, respectively, in 2011.

But the capital remains largely Australian-born, at 68 per cent of the population, despite that figure falling slightly from 71.4 per cent in 2011 - and fewer Britons called the capital home last year, down to 3.2 per cent from 3.7 per cent in 2011.