Amy Finnerty said she was more surprised than frightened when a group of teenagers surrounded her recently as she was leaving her apartment building on a tranquil street in Brooklyn Heights. The sun had not yet dropped from the sky, and she was heading to a meeting nearby at her children’s school.

“The last thing I was thinking was that I was going to get mugged,” Ms. Finnerty, 47, said. “They were so young, at first I walked away.”

The teenagers circled close, however, and grabbed her handbag, which was full of cash she had received for her birthday.

Now, after hearing other accounts of assaults, including that of a friend who was on his way to play squash when he was punched in the face by a man who leaped out from behind a car, the surprise has shifted into nervousness for herself and her two teenage daughters.

In Brooklyn Heights, assaults have risen 31% in the past two years, to 150 this year.

Robberies have also experienced a small spike: They’re up 8.1% so far this year compared with last year — although over two years the increase has only been 2.1%.

A spokesman for the New York City police department, Deputy Commissioner Paul Browne, noted that the crime rate has dropped dramatically from what it once was.

Assaults in Brooklyn Heights are down 82.5% from 14 years ago, while robberies are down 60.5%. Still, the incidents have left some residents rattled. A 17-year Brooklyn Heights resident, John Knightly, 42, has a bruise to show from a recent attack.

It happened Friday evening, after a stranger began speaking to Mr. Knightly’s companion as they walked along Atlantic Avenue. As he turned around, Mr. Knightly said he was greeted by a fist in the face. The assailant then sprinted away.

“It’s not the type of thing you expect in the neighborhood,” he said.

Some residents attribute the small rise in crime to more people living and working in Brooklyn Heights, while others say would-be robbers are attracted to the neighborhood’s wealth.

Ms. Finnerty, a writer who has had an article published by The New York Sun, said she was satisfied that police were doing a good job to address the problem, however. She said officers returned her bag after finding it stashed near the sight of her mugging — with her birthday cash still inside.