The woman demonstrated "questionable behaviour" Thursday afternoon while walking on Ontario Street near Pie IX Blvd., according to Montreal police.
Police say a mother was with her three children — ages two, five and seven — when a stranger approached the family and took the five-year-old boy in her arms and walked away.
The mother and a witness immediately grabbed the boy back. He was not injured.
The woman was quickly arrested nearby.
Police say the woman, who appeared in court Friday, will be asked to undergo a psychiatric evaluation.