The moves comes at the direction of the chief of reserves and cadets after the attacks in Ottawa and Quebec.
National Defence spokesman Daniel Blouin says while there is no indication that cadets or rangers are at risk, the precautions are being taken to ensure the safety of the youth entrusted to their care.
He says the activities are on hold through the weekend and the situation will be re-evaluated next week.
Military bases across the country are under tighter security.
Canadian Forces members have also been told to stop wearing their uniforms in public, with the exception of going back and forth to work.