South Australian police say they have concerns for the welfare of three children who were last seen 17 days ago and are believed to be with a woman known to them.

Police issued a call for information on Saturday night for the whereabouts of the three children — Zayden, Izaha and Noah — who were last seen at a Gilberton address around 1pm on May 22.

Zayden is almost three-years-old, Izaha is 16 months old and Noah is three months old.

Police said the three boys, from Black Forest, are believed to be with a woman known to them.

"Police have concerns for the welfare of the children," SA Police said in a statement.

"The three children are believed to be with a woman known to them who is described as Caucasian, aged in her early 20’s, 165cm tall with a medium build and long brown hair."

Police said anyone with information on the whereabouts of Zayden, Izaha and Noah is asked to call police immediately on 131 444 and quote reference #135439.

Source: Australian Broadcasting Corporation.