Long Island University’s administration and the union that represents about 400 faculty on its Brooklyn campus have a new employment agreement, officials announced Thursday, ending months of contentious negotiations that included a historic 12-day lockout of professors in September.

The Long Island University Faculty Federation voted 188-84 to ratify the five-year contract on Tuesday, just days before the university’s graduation ceremonies. LIU Post holds commencement on the Brookville campus on Friday; LIU Brooklyn will hold its ceremony at Barclays Center on May 11.

“Given a tumultuous year at the university — including the marred history of being the first faculty in the United States to be locked out by its own employer in September — the majority voted the contract up,” said Jessica Rosenberg, the union president. “However, the union recognizes that much work is needed to improve labor relations for the betterment of the LIU Brooklyn community.”

LIU President Kimberly R. Cline, in a statement, said, “This long-term agreement speeds our momentum at LIU Brooklyn. We are working together with faculty to pursue innovation and provide academic excellence. We value our faculty who are critical to maintaining our upward trajectory.”

Cline declined a Newsday interview request Thursday.

The two sides began negotiating in February 2016. The talks turned bitter by Labor Day weekend when unionized faculty members were restricted from accessing their offices and email accounts. Other actions including a student walkout and rallies supported by the American Federation of Teachers, one of the largest education unions in the nation.

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Administrators and instructors from LIU Post plugged in to cover classes during the 12 days that Brooklyn faculty were unable to conduct classes. The move also angered students who said the substitutes were unqualified to teach certain subjects.

The lockout ended when the administration and the union agreed to extend the last contract — which had expired on Aug. 31 — to May 31.

The employment agreement provides for 1.75 percent raises in each of the first three years and a 2.25 percent salary increase for each of the last two years for Brooklyn faculty members who are at or above the salary level of faculty on the LIU Post campus.

In addition, there are various increases for Brooklyn faculty who earn less than the Post faculty, aiming to create parity between the two — a win for union officials who have contended that professors and instructors on the Brooklyn campus earn significantly less than their Long Island counterparts.

Rosenberg said it “narrows a wage gap between the Brooklyn and Post full-time faculty and serves as an explicit recognition of a long-standing pay inequity between the two faculty bodies.”

Current undergraduate and graduate student enrollment at LIU Brooklyn is about 8,000, while at LIU Post that number is nearly 9,300, a university spokesman said Thursday.

Faculty at the Brooklyn and Brookville campuses are represented by different collective bargaining units and are not on the same negotiating schedule. LIU Post faculty are covered by a five-year contract that ends in 2020.

Both unions voted no-confidence in Cline in September.