At the beginning of 2017, there were 17,531 families with children in Helsinki where at least one parent (or the single parent) had a foreign mother tongue. They made up 23 per cent of all families. Some of these families had no children under the age of 18. The number of families with at least one child under 18 years of age and at least one parent with a foreign mother tongue was 15,319, or 25 per cent of all families with under-aged children.

There are fewer families with no children under 18 years among families with a foreign mother tongue than other families. The proportion of such families was 23 among families where both parents (or the single parent) had a national mother tongue and 13 per cent among families with at least one parent with a foreign mother tongue. The difference is partly explained by the younger age structure of the population with a foreign mother tongue.

Families with a foreign mother tongue had more children. The overall average number of children in families with children in Helsinki was 1.66. On average, there were 1.7 children in families with two parents with a national mother tongue and 2.07 children in families with two parents with a foreign mother tongue. Families with small children and families with at least 3 children were more common among families with a foreign mother tongue.