According to O Globo, a 90-ton beam fell at the construction site killing 25-year-old Juracy Cunha da Silva.
The monorail, which will connect Congonhas airport with some of the city's other metro lines, was supposed to be completed for the 2014 World Cup. Because of delays, it won't be finished until the second half of 2015.
The 11-mile-long monorail cost $1.4 billion, O Globo reports.
The death comes after three people were killed building Sao Paulo's Itaquerao stadium. The venue saw numerous delays, but should be completed by the opening game on Thursday.
Traffic has been an issue in Sao Paulo as the World Cup approaches. Because of a subway workers strike earlier this week, foreign journalists and tourists were greeted by 140-minute taxi lines at the city's two main airports. U.S. men's national team goalie Tim Howard, who's staying in Sao Paulo with the U.S. camp, also mentioned the traffic in an interview with the AP.