The 74-year-old was convicted in May 2016 by the Extraordinary African Chambers, a body created by Senegal and the African Union.
He was sentenced to life in prison following a 17 year campaign for justice by victims and rights campaigners.
The sentencing of the former leader was hailed as a landmark for the continent.
Nevertheless, Habre has refused to recognise the court’s authority. Furthermore, his court-appointed lawyers have requested an appeal on his behalf.
The hearing is expected to last several days and the final decision expected by April 30.
If his conviction is upheld, Habre will serve his sentence in Senegal or in another AU country.