The bill was approved by 136 votes in favor, 78 against and 4 abstentions.
Citizens over the age of 18 can seek help to die if they are in the final stages of an illness and suffering from "persistent" and "unbearable" pain, unless they are mentally incapable of making such a decision.
The procedure will be possible for the country's citizens and legal residents, in order to avoid the possibility of citizens from other countries traveling to Portugal to receive medical assistance in order to end their lives.
The law must now be ratified by President Marcello Rebelo de Souza, a conservative. He has stated that he will respect the decision of the parliament.
Some criticized the timing of the vote, with the opposition PSD claiming that due to the new coronavirus pandemic in Portugal, "there is a great deal of anxiety, a great deal of fear among the people about life and death."
In a letter to the Portuguese parliament, two associations that manage most of Portugal's care centers that have been hit hard by the pandemic claimed that "euthanasia approval is disrespectful to all these people".
However, Pessoas-Animais-Natureza (PAN) parliamentary spokeswoman Ines Real said: "It is dishonest to refer to an extremely difficult period in the country… to confuse the deaths associated with Covid-19 with the legislative process that aims to allow euthanasia to those who suffer ".
Portugal, a Catholic country, legalized abortions in 2007 and allowed same-sex marriage in 2010.