Along with eight other campaigners, Mr Saro-Wiwa was convicted of murder, then hanged in 1995 by the then-military regime.
Many believed the activists were being punished for leading protests against the operations of oil multinationals, particularly Shell, in Nigeria's Ogoniland. Shell has long denied any involvement in the executions.
Though the pardons have been welcomed, some activists and relatives say they do not go far enough.
As well as issuing the pardons on Thursday, Nigerian President Bola Tinubu bestowed national honours on Mr Saro-Wiwa and his fellow campaigners, who were known as the Ogoni Nine.
The nine men - Mr Saro-Wiwa, Barinem Kiobel, John Kpuinen, Baribor Bera, Felix Nuate, Paul Levula, Saturday Dobee, Nordu Eawo and Daniel Gbokoo - were among dozens who received the honours as part of Nigeria's annual Democracy Day.
Tinubu said the accolades recognised "heroes" who had made "outstanding contributions " to the nation's democracy.
Responding to the pardons for the Ogoni Nine, campaign groups said they would like the government to take further steps.
The Movement for the Survival of the Ogoni People (Mosop), which was formerly led by Mr Saro-Wiwa, called the pardon a "courageous act".
However, Mosop also said that the pardon implies wrongdoing, while in reality "no crime ever took place".
Barinem Kiobel's widow expressed her gratitude to Tinubu for the national honour, but called on the president to "properly declare [her] husband and his compatriots innocent" because a "pardon is not granted to the innocent".
Likewise, Amnesty International said clemency falls "far short of the justice the Ogoni Nine need".
More must be done to hold oil companies to account for environmental damage currently occurring in Nigeria, the organisation added.
Mr Saro-Wiwa, who was one of Nigeria's leading authors, led the Ogoni people in peaceful demonstrations against Shell and other oil companies.
Mosop accused the multinational company of polluting the land that locals relied on for their livelihoods.
The Nigerian government responded by brutally cracking down on the protesters. The Ogoni Nine were subsequently found guilty by a secret military tribunal of the murder of four Ogoni chiefs.
Their execution sparked outrage within the international community. It was widely condemned as extrajudicial murder and became a global symbol of the struggle against environmental injustice and repression.
Nigeria was consequently suspended from the Commonwealth group of nations.
Since then, Shell has faced various lawsuits over oil spills and environmental damage in the Niger Delta, the southern region that Ogoniland is a part of.
In 2021 a Dutch court ordered Shell to compensate farmers for spills that contaminated swathes of farmland and fishing waters in the Niger Delta. The company agreed to pay more than a hundred million dollars.
Earlier this year, lawyers representing two Ogoniland communities argued in London's High Court that Shell must take responsibility for oil pollution that occurred between 1989 and 2020.
Shell denies wrongdoing and says spills in the region have been caused by sabotage, theft and illegal refining for which the company says it is not liable.
The case's full trial is set for 2026.
Responding to the pardons for the Ogoni Nine, campaign groups said they would like the government to take further steps.
The Movement for the Survival of the Ogoni People (Mosop), which was formerly led by Mr Saro-Wiwa, called the pardon a "courageous act".
However, Mosop also said that the pardon implies wrongdoing, while in reality "no crime ever took place".
Barinem Kiobel's widow expressed her gratitude to Tinubu for the national honour, but called on the president to "properly declare [her] husband and his compatriots innocent" because a "pardon is not granted to the innocent".
Likewise, Amnesty International said clemency falls "far short of the justice the Ogoni Nine need".
More must be done to hold oil companies to account for environmental damage currently occurring in Nigeria, the organisation added.
Mr Saro-Wiwa, who was one of Nigeria's leading authors, led the Ogoni people in peaceful demonstrations against Shell and other oil companies.
Mosop accused the multinational company of polluting the land that locals relied on for their livelihoods.
The Nigerian government responded by brutally cracking down on the protesters. The Ogoni Nine were subsequently found guilty by a secret military tribunal of the murder of four Ogoni chiefs.
Their execution sparked outrage within the international community. It was widely condemned as extrajudicial murder and became a global symbol of the struggle against environmental injustice and repression.
Nigeria was consequently suspended from the Commonwealth group of nations.
Since then, Shell has faced various lawsuits over oil spills and environmental damage in the Niger Delta, the southern region that Ogoniland is a part of.
In 2021 a Dutch court ordered Shell to compensate farmers for spills that contaminated swathes of farmland and fishing waters in the Niger Delta. The company agreed to pay more than a hundred million dollars.
Earlier this year, lawyers representing two Ogoniland communities argued in London's High Court that Shell must take responsibility for oil pollution that occurred between 1989 and 2020.
Shell denies wrongdoing and says spills in the region have been caused by sabotage, theft and illegal refining for which the company says it is not liable.
The case's full trial is set for 2026.
By Wedaeli Chibelushi, BBC
