The decision to pay the first part of the Sala transfer fee was made by the world governing body, Fifa.
Argentine soccer player Sala died in a plane crash while travelling to join his new club.
The appeal was heard in Lausanne by a three man panel.
The first part of the money must be paid to Nantes.
The decision of the Court of Arbitration in Sport was disappointing for the Bluebirds.
The important question of FC Nantes' liability for the crash, which will have to be decided in another forum, will not be decided by the award.
We will not make any payments to FC Nantes until the club's lawyers have a better idea of why the decision was made.
The club will take legal action against those responsible for the crash if the appeals are not successful. FC Nantes and its agents will also be included.
The club put in place a trust for the family and all of our thoughts are with them.
After taking into account all the evidence produced and all the arguments put forward by both clubs, the panel found the player's transfer from FC Nantes to Cardiff City FC to have been completed.
The conditions set out in the transfer agreement were fulfilled prior to the player's death, so FC Nantes' claim for the first part of the transfer fee was upheld.
The Court of Arbitration for Sport has rendered a decision on the case.
The decision rendered by Fifa regarding the transfer of player Emiliano Sala has been confirmed by the Cas.
The court ruled that the player's transfer to Cardiff City was over when he died in an aviation accident.
Cardiff City was sentenced to a historically high sum for paying the transfer fee to FC Nantes and for procedural costs.
It has been difficult for those close to Emiliano to deal with this procedure which has been delayed many times.
The FCN has never reacted to the misinformation campaign out of respect for the player's family.
The deal was not legally binding, as they claimed, and they refused to make interim payments because they were not liable for any of the fee.
The first part of the money should be paid to Nantes.
If the club failed to pay, a three-window transfer ban would be imposed.
They appealed after they were found against them. The hearing took place in March.