Three weeks of strikes at Yale University came to an end Thursday with the announcement of an eight-year contract aimed at increasing worker benefits and creating stability for the school.

The 23-day work stoppage by secretaries, custodians, technical workers and dietary employees led to the closing of most dining halls and included picketing, sometimes with bullhorns, outside classroom buildings.

The new contracts, which are retroactive to Jan. 2002, will provide workers with annual raises of 3 to 5 percent and an increase in pensions, among other benefits.

According to the university, workers who spend at least 30 years on the job will receive an average pension increase of 40 percent.

Almost 1,000 of the unions’ workers are expected to retire before 2010, which made pensions a central issue in the negotiations.

A pay raise was also a central issue, with Yale’s unions often pointing to Harvard’s higher wages as an example the university should follow. Yale officials, however, said that the cost of living in Cambridge is higher than in New Haven, making comparisons faulty.

The long-term contract will also serve as some guarantee for Yale that labor strikes, which have plagued the university frequently over the last 35 years and twice within the last year, will not recur in the immediate future. The contracts are the longest ever negotiated with Yale workers.

Local 34, which includes secretaries and technical workers, voted Friday to accept the contract offer by a 756-10 tally. The custodians and maintenance workers of Local 35 ratified the offer after a 535-11 vote.

Both sides seem to be pleased with the outcome.

“Yale and its unions eventually reach good contracts, but not without conflict and disruption,” Yale University President Richard C. Levin said in a written statement. “These agreements will ensure that Yale has the quality workforce it needs to support its critical educational and research missions.”

Locals 34 and 35 returned to work yesterday. The unions’ votes to accept the contracts were met with jubilation.

“It’s the best contract we’ve gotten in my 30 years here,” Local 35 President Robert Proto said. “They were very pleased, very happy.”

New Haven Mayor John DeStefano Jr. had assumed the role of mediator in the negotiations, and it was he who announced the agreement Thursday at a City Hall press conference.

The strikes had attracted such notable figures as Democratic presidential candidates Joseph I. Lieberman and Howard Dean, both Yale graduates, as well as the Rev. Jesse L. Jackson. All three sided with the unions during the labor dispute.

Jackson was arrested on the sixth day of the strike with over a dozen other union supporters for disorderly conduct when they obstructed traffic at an intersection in protest.

Last Monday, 151 people, including AFL-CIO President John Sweeney, were arrested during a 5,000-protester rally to support the workers.

Over 100 dietary workers at Yale-New Haven Hospital, members of Service Employees Industrial Union District 1199, turned down the hospital’s contract offer last week. The workers will return to their posts on Tuesday as negotiations continue.

—Material from the Associated Press was used in this story.

—Staff writer Alexander J. Blenkinsopp can be reached at blenkins@fas.harvard.edu.