Nutter, a 54-year-old former city councilman, was the heavy favorite over Brown, a 52-year-old former high school math teacher and Democrat who switched parties to face Nutter and barely survived a challenge in the May primary.
Democrats outnumber Republicans by a more than 6-to-1 ratio in Philadelphia, whose last Republican mayor, Bernard Samuel, left office in 1952.
With 96 percent of precincts reporting, Nutter had 133,252 votes, or about 75 percent of the ballots cast in a low-turnout election. Brown had 38,640 votes, or about 22 percent. Political activist Wali "Diop" Rahman, who was on the ballot as an independent, was a distant third.
In his re-election bid, Nutter touted the fact that homicides are down about 18 percent since his election in 2007. He also successfully oversaw the implementation of single-stream recycling and a 311 information call center, while avoiding drastic cuts to core city services during the recession.
One of his main focuses in his second term, Nutter said, will be continuing to try to get illegal guns out of the city and slow its stubborn homicide rate. Philadelphia has had 282 homicides so far this year, compared with 274 at this point last year.
"There's still too much gun violence. There's still too many people dropping out of school," Nutter said in an interview with The Associated Press. "Our work is not done yet."
In addition, Nutter said he'd use his second term to continue trying to increase literacy rates and help people find jobs and get out of poverty. "All of these issues are tied into each other," he said.
Brown and others argue Nutter hasn't done enough to reduce violent crime, noting that while progress has been made since 2007, it falls short of the goal of a 30 percent to 50 percent reduction in homicides that Nutter set at his inauguration. Brown also said Nutter hadn't done enough to improve the city's troubled school system. And she and other critics oppose Nutter's decision to push property and sales tax increases to balance the budget, along with an abandoned plan to shutter some libraries.
Brown declined to comment on Nutter's win when reached by the AP.
During the campaign, the incumbent pointed out that the national economy collapsed shortly after his election, which forced the city to make across-the-board cuts and scrap some of his proposals, including plans to add hundreds of police officers.
Jeff Kennedy, 41, a Democrat and a city recreation worker, said he voted for Nutter because, despite all the problems, the mayor seems sincere and hard-working.
"He's just trying to do the best that he can. Unfortunately, some people have to get the short end," Kennedy said, noting that he's glad to still have a job. "I think he's sincere in his efforts. He's really trying."
Others, however, found merit in Brown's criticisms.
Maria Cifone, 35, who voted for Nutter in 2007, cast a ballot for Brown this year as a rebuke of the mayor. Crime has simply not gone down enough, said Cifone, who also was irked about the scrapped plans to shutter libraries.
"They just need better financial planning," Cifone said of the city.
Another voter, Lou DeCicco, had said he was leaning toward voting Republican even though he didn't know who was running. The 78-year-old retired truck driver said he was disappointed Nutter hadn't been able to reduce crime more using the "stop and frisk" policing techniques he endorsed in 2007.
DeCicco, who voted for Nutter last time, said the incumbent also should have done more to reduce the size of government during the recession. "He ought to lay off some of the city workers," he said.