There were highly emotional scenes at the airport when Bilawal hugged his father, a party spokesman said. He then went to his Dubai residence where Benazir and other family members were waiting for him.
"This will be the first New Year the family will celebrate together for eight years," party spokesman Aijaz Durrani told AFP.
Zardari, tipped as a possible opposition leader in Pakistan, had not seen his wife since he was locked up in 1996 on murder and corruption charges.
He travelled to Dubai with youngest daughter Asifa. Whereas son Bilawal and elder daughter Bakhtawar had gone on ahead to Karachi earlier this week.
He will spend some time with the family and will also undergo a complete medical check-up before they all fly to Saudi Arabia, Durrani said.
"I will return soon to carry out the struggle for restoration of democracy," Zardari told AFP before boarding the plane in Karachi on Thursday.