The Israeli military announced that the gunman “approached the area in a truck from Jordan, exited the truck, and opened fire at the Israeli security forces operating at the bridge”.
Three Israeli civilians were pronounced dead at the scene after a military medical team had performed resuscitation efforts, the Israeli military said.
The Israeli manager of the crossing said the three customs workers were shot at close range by the driver crossing from Jordan.
The shooting took place near an Israel-controlled commercial cargo area, where Jordanian trucks offload cargo entering the West Bank from the kingdom.
Jordan has closed the Allenby Bridge crossing, also known to Palestinians as al-Karamah Bridge, until further notice as authorities investigate the incident, the interior ministry said.
The crossing, which lies north of the Dead Sea, is the only international entry point for Palestinians from the West Bank that bypasses Israel.
The attack came as Israeli violence against Palestinians in the West Bank, including military raids and settler attacks, has soared since the start of the war in Gaza on 7 October.
More than 650 Palestinians have been killed by Israeli forces or settlers in the West Bank since, according to the Palestinian health ministry.
At least 23 Israelis, including members of the security forces, have been killed in Palestinian attacks during the same period, Israeli officials say.