CUPW's foremost major strike was an illegal wildcat strike in 1965 (before public sector workers got the right to strike or form unions) & is the big illegal strike involving government employees. A action succeeded inside winning the right to collective bargaining for all public sector employees. More major industrial actions involved the strike inside 1968 and a campaign of walkouts inside 1970 that resulted in above norm salary increase. Farther strikes within 1974 and 1975 succeeded in gaining job security in a face of fresh technology at the post professional. The 1978 strike resulted in CUPW president Jean-Claude Parrot being jailed when a union defied back-to-operate legislation go past the Canadian parliament. CUPW's defiance of a law stimulated the irregular rift between it & the other conservative Canadian Labour Congress. Within 1981, after a second strike, CUPW became a number 1 federal civil service union around Canada to win the right to maternity leave for its members.

Around 1981, Canadthe Post was transformed from the government department to a crown corporation, fulfilling a long-standing require per union. It was hoped that by becoming the crown corporation governed per Canada Labour Code, relations between Canada Post and its union would improve. When strike action has been less frequent, there were rotating strikes around 1987 and 1991 against plans to privatize postal outlets, both of which were ended by back-to-act legislation & as well saw tries by Canada Post to break a strike applying "replacement workers" when it were known as by Canada Post or even "scabs" as the union known as the children.

Within 1989, the American Labour Relations Board forced totally Canada Post employees under of these union. Until that period CUPW, got delineate single "inside employees" by having a Letter Carriers Union of Canada represented "outdoor employees" & various more unions like a Union of Postal Communications Workers & a International Brotherhood of Electrical Workers representing smaller units of specialised workers inside a post professional . Fallowing a vote, CUPW was chosen across LCUC to become the resole union representing altogether postal employees.