Real Madrid, along with city rivals Atletico Madrid, were hit with bans in January 2016 after FIFA’s Disciplinary Committee found them to be in breach of regulations “relating to the international transfer and registration of players under the age of 18”.
Spanish champions Barcelona were hit with a similar sanction in 2014.
An appeal to FIFA failed in September, prompting Madrid to take their claim to CAS.
Despite CAS ruling partially in their favour, Madrid released a statement in which they outlined their displeasure at the verdict and that initially delivered by FIFA.
The two-window ban had been suspended while the investigation continued but Madrid were facing up to the prospect of not being able to register new players for the entirety of 2017.
That punishment has now been halved with the European champions able to strengthen their squad when the window opens at the end of the current season, although they will be inactive in January.