Bhutto, the Pakistan People’s Party chief and a two-time prime minister, was killed along with more than 20 people in a gun and bomb attack in Rawalpindi's Liaquat Bagh during an election campaign rally on December 27, 2007. She was 54.
The anti-terrorism court (ATC) this week acquitted five Tehreek-i-Taliban Pakistan suspects due to lack of evidence in the case.
It, however, sentenced two senior police officers to 17 years in jail and declared former dictator Pervez Musharraf a fugitive and ordered authorities to seize his properties.
A joint investigation team had implicated Musharraf in the case, saying his government did not provide adequate security to Bhutto during the rally despite her repeated requests.
"We are not satisfied with the verdict, we will appeal against it," Zardari was quoted as saying by Geo News in Nawabshah in Sindh Province after offering Eid prayers.
After the ATC judgment on Thursday, Bhutto's daughter Aseefa Bhutto Zardari had tweeted: "There will be no justice till Pervez Musharraf answers for his crimes."
Zardari's Pakistan People’s Party (PPP) has rejected the ATC judgment as "disappointing" and has said the party will explore legal options to challenge the verdict.
It has said that acquitting al-Qaeda and Taliban suspects despite evidence was shocking.