TTIP, or the Trans-Atlantic Trade and Investment Partnership, is a hotly contested free trade deal between the European Union and the United States that critic say is anti-democratic and would lower food safety, working and environmental standards if passed.
Organizers have scheduled public rallies in Stockholm, Gothenburg, Malmö and in several other cities on Saturday.
"It's an undemocratic agreement that threatens to hand the powers over virtually all aspects of our lives to big corporations," Brenda El Rayes, a campaigner for the Swedish group Skiftet, which opposes the deal, tells Radio Sweden.
The protests were part of a week-long push throughout Europe that began on the weekend. On Saturday, hundreds of thousands of people marched in Berlin against the deal.
In Stockholm's central Mynttorget square, an afternoon rally was set to feature Green Party member of parliament Carl Schlyter and representatives of the cosmetic company LUSH speaking out against the plan.