Gov. Rick Perry, R-Texas, and a group of local dignitaries were the first to ride across the repaired bridge after the official ribbon cutting ceremony. Earlier they observed a brief moment of silence to remember the eight people killed when a barge knocked a section of the bridge down.
Businesses on the popular resort island have suffered since the accident because only ferry service was available to bring tourists to the island.
State Sen. Eddie Lucio, D-Brownsville, called it a "proud and glorious day" for the whole state.
"I'm thankful for the hundreds of people who will return to work, and have great concern for their families who have suffered economic hardships," he said.
The $4 million bridge repair was completed a month ahead of schedule.
The causeway was heavily damaged Sept. 15 when several sections of the bridge fell into the Laguna Madre, killing eight motorists whose cars fell more than 90 feet into the water. A barge struck the bridge and an investigation is still underway into the cause of the accident.
Although the federal government has shared in the cost of repairing the bridge and provided Small Business Administration loans for businesses, the Federal Emergency Management Administration has refused to provide special disaster unemployment funds.
Earlier this week, Perry appealed the FEMA ruling to President George W. Bush because he said the funds were needed for those ineligible for state unemployment benefits.