Six Turkish citizens, two members of three families, were killed in the attack on November 13, 2022.
The explosion also injured about 100 people in the busy street packed with shoppers and tourists.
The court imposed a total of seven life sentences on Albashir, who was previously identified by police as the person who planted the bomb.
The case also involved more than 30 other defendants.
Four of them were released from prison on Friday, while the court ordered 10 defendants to be tried separately as the individuals could not be found.
Twenty other defendants were handed prison sentences ranging from four years to life.
Of those 20, six people were given aggravated life imprisonment sentences for "disrupting the unity and integrity of the state" and "intentional murder".
Turkey blamed Kurdish militants for the explosion, saying the order for the attack on Istiklal Avenue was given in Kobani in northern Syria, where Turkish forces have conducted operations against a Syrian Kurdish militia in recent years.
That militia and the outlawed Kurdistan Workers Party (PKK) militant group, which has fought a decades-old insurgency against the Turkish state, denied involvement in the attack.
No group claimed responsibility.
Istanbul has been attacked in the past by Kurdish, Islamist and leftist militants.
A wave of bombings and other attacks began nationwide when a ceasefire between Ankara and the PKK broke down in mid-2015.
More than 40,000 people have been killed in the PKK's conflict with Turkey since the militant group took up arms in 1984.
It is considered a terrorist organisation by Turkey, the European Union and the US.
