Usually, a castellan combined the duties of both a majordomo (responsible for a castle's domestic staff) and a military administrator (responsible for maintaining defenses and protecting the castle's lands). This was particularly the case if there was no lord resident at the castle, or if the resident lord was frequently absent.
At times, there was a castellan among the Officers of the Kingdom of Jerusalem.
Karō (家老) were top-ranking samurai officials and advisors in service to the daimyo of feudal Japan.
In the Kingdom of Poland and later the Polish-Lithuanian Commonwealth, the Castellans (Polish: Kasztelan) were in most cases lower in precedence to the voivodes (with the exception of the Lord Castellan of Kraków who had precedence before voivode of Kraków). Castellans were in charge of a part of a voivodeship called Castellany (Polish: Kasztelania) until the 15th century and from that time on their domain was divided into provinces for Greater Castellans and powiats for Minor Castellans. Castellans in the Polish–Lithuanian Commonwealth were of senator rank.
In Portugal, a castellan was known as alcaide. Later, the role of alcaide became an honorary title awarded by the King of Portugal to certain nobles. As the honorary holder of the office of alcaide did not often lived near its castle, a delegate of him started to be appointed to effectively govern it. An honorary holder of the office became known as alcaide-mor (major alcaide) and its delegate became known as alcaide pequeno (little alcaide) or alcaide-menor (minor alcaide).
See also 
- Friar, Stephen (2003). The Sutton Companion to Castles, Sutton Publishing, Stroud, 2003, p. 47. ISBN 978-0-7509-3994-2.