Since the official census count in May 2010, the city has added an estimated 21,601 people for a total of 1,547,607.
In contrast, between 2000 and 2006, Philadelphia lost nearly 29,000 people.
The growth is due in part to births outpacing deaths and an influx of international migration, the census data show.
"Philadelphia keeps moving in the right direction," said Mayor Nutter. "The dynamism, innovation, and diversity of our population is attracting new people to Philadelphia and encouraging residents to want to stay in one of the greatest cities in America."
While more people "contribute to greater income, spending, tax revenue, and vibrancy," Philadelphia lacks the industries that would attract large increases of workers from around the country, said David Elesh, an urban sociologist at Temple University.
"Most of our growth has to come from foreign immigration," he said.
In Philadelphia's eight-county region, only Chester County grew faster than the city between 2010 and 2012, adding 7,689 people, an increase of 1.5 percent.
During the same period, Philadelphia's increase was 1.4 percent. Montgomery County followed with an additional 8,586 people, a change of 1.1 percent; Bucks grew by 1,804 or 0.3 percent, and Delaware County by 2,119 or 0.4 percent.
In New Jersey, while Burlington County added 2,602 people (0.6 percent) and Gloucester County 1,298 (0.5 percent), Camden County's population dropped by 118.
Neither Pennsylvania nor New Jersey saw dramatic growth.
Neither state is home to the 100 fastest growing counties with at least 10,000 residents. Texas has 17.
The Philadelphia metro - a census-defined area that includes South Jersey and Wilmington - surpassed six million people in 2012, an increase of 53,459 or just under 1 percent.
While that growth is welcomed, it lags other major metros.
As a result, Houston overtook Philadelphia's as the fifth most populated metro area.
Metro Houston grew from 2010 to 2012 by 4.3 percent to 6,177,035.
Ryan Sweet, senior economist for Moody's Analytics, warned against comparing Philadelphia with Houston because the Texas economy has benefited from the energy industry. While Philadelphia's job market is diverse, there are drawbacks.
"The tax structure," he said, "has proven to be a hurdle. But there are signs that the city is addressing some of those issues, which is encouraging."
Looking ahead, Philadelphia could get bumped by the Washington metro area, whose population climbed 4 percent to 5,860,342.
One variable is that the capital's population ebbs and flows depending on federal spending.
Contact Dylan Purcell at 215-854-4915 or firstname.lastname@example.org or follow on Twitter @dylancpurcell.
Inquirer staff writer Melissa Dribben contributed to this report