DUBAI—Saudi Binladin Group laid off 50,000 people, according to a person briefed on the plans, as the construction giant attempts to turn around a business hammered by low oil prices.

The scale of the retrenchment means the Jeddah, Saudi Arabia-based conglomerate cut nearly a quarter from its workforce of about 200,000. The people who were laid off, mostly construction-site workers from Asia, have been paid their outstanding salary and dues, according to the person familiar with the situation.

...