Two men in their 60s – one from Messines (Silves) and the other from Castro Verde (Alentejo) – were killed in a head-on crash on the IC1 national road between Lisbon and the Algarve.
The accident happened at around 7.48pm on Wednesday near Santana da Serra, Ourique.
According to national tabloid Correio da Manhã, the truck driven by Messines resident António Carrasqueiro, 61, veered into the opposite lane of the road.
The other driver, 60-year old Jorge Nunes, tried to avoid the crash by swerving to the side of the road but to no avail.
By the time firefighters arrived, both men were already in cardiorespiratory arrest. Resuscitation efforts were unsuccessful, Ourique fire commander Mário Batista told CM.
Traffic was cut off for around one hour.
GNR police are investigating the cause of the accident.