In addition the NUJ, which allows public relations professionals to join its ranks of more than 30,000, will offer its members a discount on PRCA membership.
Francis Ingham, PRCA director general, said: "I know how valuable the union's support has been in making the case for ethical and properly regulated lobbying. I'm keen to let NUJ members see that the PRCA can offer them valuable extra benefits and can support their professional career in parallel to the union's support."
The new agreement would include a number of "high-profile campaigns" with further details to be announced in the coming months, added PRCA director of communications Matt Cartmell.
"There is a well-trodden path that runs between PR and journalism and it’s about time someone recognised that," he said.
"We’re looking for common ways of tackling key issues and working together, whether that is on policies increasing diversity in our respective industries or transferrable ethical guidelines."
NUJ general secretary Michelle Stanistreet added: "As the trade union representing workers in the industry we want to make the most of opportunities to work with others who are involved with the public relations industry where we can.
"The PRCA has done excellent work highlighting the need to make public relations more reflective of the population it serves and we know this is an area of common ground."
Earlier this month the PRCA and PRWeek launched Internships For All in an effort to boost diversity in PR.