Saint-Jacques studied engineering physics, astrophysics, and medicine before becoming a physician in remote communities and a CSA astronaut. That mix of science, engineering, and clinical experience shaped his ISS mission role.

He launched on Soyuz MS-11 and served aboard the ISS during Expeditions — open definition 57, 58, and 59, completing a single long-duration mission built around station research, medicine, robotics, and operations.

Saint-Jacques's spaceflight career is defined by the combination of scientific training, medical practice, and a long-duration Canadian presence aboard the International Space Station — open definition.

Soyuz MS-11 launched on December 3, 2018 aboard Soyuz MS-11 flight vehicle, with Saint-Jacques serving as Flight Engineer — open definition. This mission context is drawn from the linked agency or institutional flight material and distinguishes flown service from training or backup assignments.