In the past five years, the number of working children between the ages of 10 and 17 has doubled to 9,700 in the territory, according to the Palestinian Bureau of Statistics.
The bureau said 2,900 of those children are below the legal employment age of 15. Economists in the narrow coastal strip estimate the real number of underage workers could be twice as high.
The increase in Gaza goes against trends. The International Labor Organization says the worldwide number of children in labor has fallen by a third since 2000, from 246 million to 168 million, with more than a fifth in sub-Saharan Africa.
At one garage in downtown Gaza, 16-year-old Mahmoud Yazji and another boy, aged 12, work nine hours a day. Mahmoud said he earns the equivalent of $13 a week; the younger boy takes home half of that.
"My father makes NIS 1,000 ($258) a month. It disappears in a few days, and we struggle for the rest of the month," Mahmoud said.
Haitham Khzaiq, 16, quit school six months ago to sell candy apples to visitors at Gaza's newly developed seaport, a major picnic venue. He works a half-day, seven days a week, and said he earns a total of NIS 20 ($5).
"We are five brothers and eight sisters. I am the oldest son, and I had to work because my father is unemployed," he said. "I don't earn enough but it is better than nothing and it is better than begging people for money."
A devastating 2014 war between Palestinian militants and Israel, border restrictions imposed by Israel and Egypt and the destruction of cross-border smuggling tunnels by an Egyptian government at odds with Gaza's Hamas rulers have contributed to economic hardship in the territory.
The United Nations estimates that 80 percent of the population is aid-dependent, with unemployment rising to its current level from around 35 percent five years ago.
"Some people are living like kings, and many others like us are hardly finding anything to eat," said 10-year-old Mohammed, who sells potato chips on the street and began working after his father, a construction labourer, lost his job.
A gap is evident on the Gaza beachfront, where child vendors lugging trays of tea, coffee and snacks mingle with other children using expensive cellphones to record their family picnics. Several nice hotels overlook the port and beachfront.
A Dutch-funded organization, El-Wedad Society for Community Rehabilitation, has been running a project for three years aimed at convincing families in Gaza of the importance of returning working children to the classroom.
"We are very worried. We feel children's rights are being trampled on," said Naeem al-Ghalban, who heads the society.
Its representatives visit the homes of working children they meet on the street and invite them to guidance sessions at the organization's headquarters. Children are taken for visits to Gaza's colleges to show them what could lie ahead if they go back to school.
Ghalban said that over the past three years, some 50 working children have taken up their studies again as a result of the organization's efforts.
"We have managed to persuade some families that educating their children is far better and more valuable than the little money they make," he said.