Maria Zabranska disappeared on Monday when her mother, Marcela Zabranska, picked her up from her St-Jean-sur-Richelieu, Que., home and never brought her back.
The child normally lives there with her father, who is her primary custodian. Her mother lives in the Czech Republic.
Zabranska is believed to have returned to the Czech Republic with Maria in tow, Sûreté du Québec investigators confirmed on Tuesday.
Police are still investigating how a woman could have left Canada with a child she does not have custody of.