The technical workers had voted Feb. 19 to reject the same offer. The workers' union, the Society of Professional Engineering Employees in Aerospace, had cautioned that a second rejection would "almost certainly" lead to a lengthy strike since Boeing had refused to improve its offer.
The latest vote was 4,244 to accept and 654 to reject, union spokesman Bill Dugovich said.
The union made no recommendation this time, after earlier urging both the 7,200 technical workers and the 15,500 Boeing engineers it represents to reject the pact. Engineers and technical workers bargain at the same time but their contracts are separate and independent agreements.
The engineers approved their contract offer in the first vote. It contained the same pension provision for new hires.
Chicago-based Boeing said it was pleased with the latest vote results. It has said a switch away from pensions is vital to the company's competitiveness.
"The votes by technical workers and engineers in recent weeks will allow us to come together and focus on the challenges and opportunities we face this year," said Ray Conner, president and CEO of Boeing Commercial Airplanes. "We're moving forward with an excellent team in place."
The technical workers narrowly rejected the offer in their first vote, 3,203 to 2,868.
SPEEA earlier told the workers that the contract offered a number of pluses, including locking in contract terms for four years that include "5 percent annual wage pools, maintaining medical benefits without increases and an improved basic retirement benefit calculation for existing techs in pension," the message said.
The union's approximately 23,000 employees are mostly in the Puget Sound region, working on jetliner design and technical issues. Factory assembly work is done by members of the International Associations of Machinists. The machinists approved a four-year contract in December 2011.
SPEEA and Boeing started negotiations in April 2012, the union said. Technical workers have been without a contract since Nov. 25.