The ICC said the ex-president is on a conditional release in Belgium, pending a possible appeal.
Mr Gbagbo is expected to stay with his second wife and child in Belgium until he is completely set free.
His prosecutors said he had clung to power "by all means" and they charged him with four counts of crimes against humanity, murder, rape and other forms of sexual violence, persecution and "other inhumane acts."
However, ICC judges ruled last month that he had no case to answer and ordered his immediate release.
The court records show that there was "insufficient evidence" to convict Mr Gbagbo of crimes against humanity.
Mr Gbagbo has emerged the first former head of state to stand trial at the ICC.
The former leader was charged with crimes against humanity following a disputed 2010 election that left 3,000 people dead and 500,000 displaced.
The violence in Ivory Coast came after Mr Gbagbo refused to accept that he had lost a disputed election run-off to his rival Alassane Ouattara.
UN and French-backed forces eventually captured Mr Gbagbo in a presidential palace bunker in 2011.