The falling machine damaged parts of the stand at the Arena Corinthians.
Stadium owner Corinthians FC said: “The accident resulted in the death of two workers – Fábio Luiz Pereira, age 42, who was a driver/operator and Ronaldo Oliveira Santos, age 44, who was a setter.
“The crane which was holding the last module of the structure’s metallic cover fell over the circulation area of the east building.
“It damaged the front of the stadium, although the grandstand’s structure was not compromised.
“It was the 38th time that this type of process was made during the construction and a similar piece with equal proportion was set less than a week ago in the south area of the stadium.”
The venue is being built by Brazil’s Odebrecht Infrastructure company, who recently said the arena was about 94% ready.
The stadium was due to be completed at the end of December to meet a Fifa deadline.
Brazil has admitted it is struggling to have all 12 venues ready for the tournament.
To see the aftermath of the collapse on a BBC report click here