Behind the wheel of his No. 5 Tatuus FA10B, Stroll set a 1m19.159 on lap 5 at the average speed of 166.3 km/h on the Miami-Homestead road course.
Stroll, fresh out of international karting, clinched his maiden pole in this series, qualifying ahead of Antonio Fuoco and fellow countryman Nicholas Latifi of Toronto.
A field of 12 cars will take the green for this race of 30 minutes plus one lap of the 3.657km circuit.
Stroll qualified second behind Fuoco for Race 2.