CHICAGO—A concerted effort here to reduce violent crime during the Memorial Day weekend appears to have led to a drop in shootings.

Increased police presence across the nation’s third-largest city and raids targeting gangs helped drive a reduction in violent crime, authorities said, with about a third fewer people shot than during the holiday weekend last year.

As of 11:59 p.m. Monday, 44 people had been shot in 33 incidents since Friday evening, compared with 61 people shot in 47 incidents over the same period last year.

Last year’s violence over the Memorial Day weekend was the start of a bloody summer in the city. The year ended with more than 4,000 shootings and 762 homicides, the largest single-year increase in violent crime that any of the five largest American cities had experienced in at least 25 years.

The drop this holiday weekend suggests police are having initial success in bringing down violent crime through stepped-up enforcement and cooperation with federal agencies.