Boston Mayor Michelle Wu is endorsing Enrique Pepén over incumbent Ricardo Arroyo in the District 5 City Council race, she announced Monday.

"I've seen his work ethic," Wu told GBH News in an interview. "I've seen how much he cares and will chase down any little detail that's needed to make sure city services happen for our residents."

Pepén was born and raised in Boston and previously served as Wu's director of neighborhood services. He told GBH News he was pleasantly surprised with the endorsement from Wu, who lives in the district he would represent if elected.

"Not only does it feel like an endorsement from the mayor, but as a resident, too," Pepén said.

"I hope that this endorsement shows that I'm here for coalition building," he added. "I want to make sure I'm representing every corner of the district, that I'm listening to every voice."

Wu's snub to Arroyo comes as he's been embroiled in a number of issues, including an ethics violation and ongoing infighting on the council.

She endorsed him during his first run in 2019. She also voted for him in the Suffolk County district attorney race, even after withdrawing her endorsement over past sexual assault allegations that resurfaced during the race, she said on GBH’s Boston Public Radio.

When asked about Arroyo, Wu said, "I'm sharing the decision I've come to looking at the field of candidates and evaluating what the needs are for the district and for the City Council in this moment."

She said the "steady flow of unfortunate headlines" related to the City Council have been distracting.

Arroyo said in a statement, "I am proud to be the only candidate in this race with a proven independent and progressive record. Like the residents of District 5, I am focused on the issues that impact their daily lives and will continue to be a champion for racial, environmental, economic and social justice."

When asked about the recent tension on the City Council, Pepen said, "We need to put the residents first. I'm ready to work with every councilor in that chamber and including our mayor to make sure that we're putting our differences aside and that we're working for the betterment of the residents' life. I think that we've gotten away from that a little bit."

Pepén has previously worked for Sen. Elizabeth Warren, former Rep. Joe Kennedy III, former Mayor Marty Walsh and former City Councilor Tito Jackson.

The preliminary election is on September 12, and residents can vote early starting Sept. 2. The four way race will also include candidates Jean-Claude Sanon and Jose Ruiz.