"I will listen. I will learn. I will lead," Walsh said in his inaugural address at Boston College, his alma mater.
The former Democratic state representative and onetime labor leader called Boston a city of courage, of champions and of big dreams, noting that he was once just a kid from the city's Dorchester neighborhood and joking that even his mother was surprised at how far he had come.
Walsh, 46, outlined a series of broad policy goals, including improving public safety and ending "senseless gun violence." While noting that the 40 homicides in Boston last year were fewer than the year before, Walsh said the number was still too high.
"No parent should worry that a bullet will stop a daughter or son from coming home," he said. "No woman should be scared on our streets. No senior should be afraid in their home. And no child should be forced to live with trauma and the indelible scars of violence."
Walsh also said he would work to strengthen the economy and create jobs, improve the city's schools and increase transparency at City Hall, including new conflict-of-interest and personal financial disclosure rules for city officials. He also said he would work to streamline licensing and permitting processes and restructure the Boston Redevelopment Authority, the city's lead economic agency.
Among his first challenges in offices will be choosing a new permanent school superintendent and police commissioner.
Walsh thanked Menino, who first took office in 1993, saying his "legacy is already legend and his vision is all around us."
Menino left City Hall for the last time as mayor Monday morning to applause from staffers and city workers. Later, he tweeted: "Thank you Boston. It has been the honor and thrill of a lifetime to be your Mayor. Be as good to each other as you have been to me."
Menino, 71, who has battled health problems in recent years, opted against seeking an unprecedented sixth full term as mayor of New England's largest city. He plans, among other things, to teach at Boston University in the coming year.
Gov. Deval Patrick and U.S. Sen. Elizabeth Warren were among those who spoke at the inauguration, with Patrick cautioning the new mayor about the pressures that lay ahead in the high-profile job.
"You won't remember precisely the day your jokes became so funny, when you became so photogenic, and when you were expected to have an opinion on absolutely everything," Patrick said.
Walsh, who overcame childhood cancer and struggled with alcoholism as a young adult, emerged from an initial field of 12 contenders to succeed Menino.
An inaugural celebration featuring the Boston Pops, several bands and local comedians was scheduled to be held Monday evening at the Hynes Convention Center.