The mandate was first approved by parliament in October 2014 and was renewed for another year in September 2015.
It allows military action in Turkey's two southern neighbours against Islamic State jihadists and other groups deemed by Ankara to be terror organisations.
Using the existing mandate, Turkey on August 24 launched an unprecedented operation inside Syria dubbed Euphrates Shield to back pro-Ankara rebels fighting IS jihadists and a Kurdish militia.
Ankara is also believed to have an unspecified number of troops in the Bashiqa camp outside IS-controlled Mosul in northern Iraq involved in training Iraqi fighters who plan to recapture the city.
The bill passed easily on the first day of the new session of parliament with support from the ruling Justice and Development Party (AKP), secular opposition Republican People's Party (CHP) and Nationalist Movement Party (MHP).
Only the pro-Kurdish Peoples' Democratic Party (HDP) voted against.
According to the state-run Anadolu news agency, the new mandate will run until October 30, 2017.
In his speech marking the opening of parliament, President Recep Tayyip Erdogan said the initial goal of the Syria operation was to create a "safe area free of terror organisations" some 5,000 square kilometres in size.
Erdogan hailed the results of the operation so far in the Syrian town of Jarabulus, saying its population had expanded from 2,000 to 40,000 since being captured from IS jihadists.
As well as targeting the jihadists, the operation is also aimed against Kurdish People's Protection Units (YPG) militia which Ankara regards as a terror group.
Erdogan said he believed that Mosul could be taken from IS but warned Baghdad and Turkey's Western allies that Ankara had to be involved in any operation and included in the decision-making process.
"Turkey cannot be left off the table. The others don't have such a border (with Iraq). They may want us to stay as spectators but that decision is also going to be made here."
In December, Turkey said it had sent up to 300 troops to Bashiqa camp to protect Turkish military personnel involved in training Iraqi fighters.
But this sparked a diplomatic row with Baghdad and an unspecified number were pulled back following US pressure to end the row. The current number of troops is unclear.
Turkey is also upset that the United States uses as an ally in Syria the Kurdish People's Protection Units (YPG) militia which Ankara regards as a terror group.
Erdogan said there was an "inconsistency" in the US policy with "part of the US administration working with the (YPG) and part working on policies more sensitive to our interests".
In a sign of the tensions inside Turkey, the MPs of the pro-Kurdish HDP refused to stand up when Erdogan entered and their co-leaders Selahattin Demirtas and Figen Yuksekdag were not in the chamber.
