Blazon: Per pale azure a castle triple-towered or windowed gules and of the second, a crescent decrescent argent and a lion rampant of the second
The representation of the lion and the crescent moon don’t seem consistent; some depictions, as here, have the lion almost within the curve of the moon, and in others, it looks more like the lion is supporting the moon with its front paws. The dexter half of the shield is apparently a canting element, since alcázar is Spanish for a fortified castle. The sinister half replicates the arms of Huete, to which the town previously belonged. Allegedly, the lion represents the victory of the Christians over the Muslims (represented by the crescent) in the Reconquista, but I don’t have a good source for that theory.