Casimiro started coaching CB Puertollano, and other Castilian-Manchegan teams, before joining CB Breogán in 1993, as an assistant coach of Ricardo Hevia in the Liga ACB.
Five years later, Casimiro managed TDK Manresa to win the 1997–98 Liga ACB, which is considered to be one of the biggest miracles in the history of Spanish professional club basketball.[1]
After leaving Manresa, Casimiro continued coaching in Spain, in different teams of the Liga ACB and LEB Oro.
On 25 September 2016, Casimiro led Herbalife Gran Canaria to win the 2016 Spanish Supercup title, its first ever national title.[3] In the 2017–18 season, Casimiro reached the ACB semi-finals with Gran Canaria. With this achievement, the team also qualified for the next EuroLeague season, the club's first participation ever. On 13 June 2018, Gran Canaria announced the club and Casimiro separated ways.[4]