The 58-year-old widower of former prime minister Benazir Bhutto was treated to an honor guard from the armed forces and shook hands with staff before leaving the plush presidential palace.
He was driven away in a black luxury saloon car from the sprawling residence at the foot of the lush green Margalla hills on the outskirts of Islamabad.
Never popular and always shrouded in controversy, Zardari -- once jailed for 11 years for alleged corruption -- is now likely to split his time between Pakistan and Dubai.
He retires six years after his wife's murder, having presided over the only civilian government in Pakistan to complete a full term in office and hand over to another at the ballot box.
His successor Mamnoon Hussain is to be sworn in on Monday.
A businessman and close ally of Prime Minister Nawaz Sharif, Hussain's low-key persona and lack of personal power base will put him in stark contrast to Zardari.
Zardari, who later arrived at his newly-built villa in the eastern city of Lahore, told party workers that he would further strengthen democracy by re-organizing his party.
"I want to set up new traditions. We have strengthened democracy; we have empowered women by appointing them as speaker and the foreign minister. We will further strengthen democracy by cooperating with our opponents," he said.
Zardari, whose Pakistan People's Party (PPP) suffered a humiliating electoral defeat to the Pakistan Muslim League-N (PML-N) in May, said his party was still taking the "war for democracy" ahead.
"Our mandate was stolen by the forces which want to destabilize Pakistan. But we accepted that mandate to strengthen democracy. We did not lose the war but have taken it ahead for the cause of democracy," he said.
"Now I have to fulfill your responsibilities, now I will meet workers, my sisters and brothers and will reorganize the party all across the country," he said.
He also pledged support for close ally and Prime Minister Nawaz Sharif.
"I want to tell Nawaz Sharif, we will not let you weaken. We will fight shoulder to shoulder with you against the forces which want politics of gun instead of the politics of ballot."
Aides deny that Zardari, unpopular and divisive within the PPP, will spend most of his time abroad and insist he will concentrate on trying to revive the center-left party.
The PPP ran a rudderless general election campaign and has been thrust into its greatest crisis, suffering a crushing electoral defeat without a Bhutto at its helm.
Zardari said in an interview broadcast on Saturday that he would not run as prime minister in future and would instead re-organize the party by shuttling around the country.
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