Gabriela “Gigi” Coletta, a former Boston City Council staffer, will take on a new role at City Hall after winning a special election Tuesday for the District 1 City Council seat. The area covers East Boston, Charlestown and the North End.

Coletta declared victory within an hour of polls closing Tuesday night. Unofficial results from the Boston Election Department were still pending by the time she made victory remarks to a crowd of a few dozen supporters gathered at an East Boston restaurant.

“We made some ambitious plans together, and I’m expecting every single one of you to hold me accountable to them,” she said. “I need you to come into City Hall with me.”

Coletta’s opponent was Tania Del Rio, executive director of the YWCA Cambridge and former director of the Office of Women’s Advancement.

Both Coletta and Del Rio are Democrats and residents of East Boston. The two women were running to fill a vacancy left by Lydia Edwards, who was elected to the state Senate through special election in January. Edwards endorsed Coletta, her former campaign manager and chief of staff, to succeed her.

Jorge Mendoza, a North End resident and restaurateur frustrated by Mayor Michelle Wu’s newly imposed $7,500 fee for eateries in his neighborhood to offer outdoor dining, launched a late-entry sticker campaign to represent the district. Mendoza set up an account with the state’s campaign finance agency last month as an unenrolled candidate.

Coletta raised nearly $140,000 between December and March, according to the latest figures from the state agency that oversees campaign finance.

Del Rio raised about $66,000 in the same period.

The Boston Election Department now has ten days to certify the election results, unless one of Coletta’s opponents requests a recount. Coletta will be sworn in as the District 1 City Councilor once results are made official.