William “Mo” Cowan, a 1994 graduate of Northeastern University’s School of Law, has been appointed by Governor Deval Patrick of Massachusetts to serve as the state’s interim U.S. senator.

Cowan will replace U.S. Sen. John Kerry, who resigned after 29 years in the seat to become the nation’s secretary of state. Voters will choose Kerry’s permanent successor in a special election on June 25.

“I pledge to people of Massachusetts that during this interim period I will go to work every day with the needs and aspirations of state’s citizens foremost in my mind,” Cowan said in a Wednesday morning press conference at the State House announcing his appointment. “I know the citizens of Massachusetts care about jobs, education, and affordable, high-quality healthcare and I will work with those interests in mind every day.”

“Mo is a fantastic leader with a heartfelt commitment to public service,” said Joseph E. Aoun, president of Northeastern University. “He has that rare combination of deep policy expertise and the ability to build excellent working relationships with colleagues. These talents will serve him—and Massachusetts—well in the Senate.”

Cowan stepped down as Patrick’s chief of staff last November and had previously served as the governor’s chief legal counsel. He is also a former member of the litigation section of the Boston-based law firm Mintz Levin Cohn Ferris Glosky, and Popeo, P.C. and the former president of the Massachusetts Black Lawyers Association.

At the press conference, Patrick called Cowan a trusted adviser, professional colleague, and a longtime friend. “Mo is a highly respected public citizen,” he said. “In every step, he has brought preparation, perspective, wisdom, sound judgment, and clarity of purpose. That has all earned him the respect, admiration, and trust of people throughout government.”

Cowan’s prestigious career has been widely recognized. He has been named a “Top 5 percent Massachusetts litigator” by Law and Politics magazine and a “40 Under 40” business leader by the Boston Business Journal.

His Northeastern experience helped shape his career success. “Northeastern is what brought me to Massachusetts, and I am thankful for the inspiration, lessons, and real world experience I gained during the time I spent there,” Cowan said. “It is one of many pieces that helped bring me to where I am today.”

Of his first co-op as a judicial intern with the Honorable Patti Saris of the Massachusetts State Trial Court, Cowan once said, “Getting her real-time constructive criticism of my lawyering skills in their infancy was important in shaping the lawyer that I ultimately became. I was challenged, I was pushed, and I was taught how to communicate in writing as a lawyer.”

He also noted that his second co-op with North Carolina Prisoner Legal Services taught him an important lesson in litigation. “It helped me realize that as an advocate you often have to place personal feelings on the back burner to advocate for your client or to ensure that justice is done.”