The present disclosure relates to an antenna assembly, which comprises: a feeder panel; an array of radiating elements mounted on the feeder panel; an array of parasitic elements mounted on the feeder panel, in which, at least a portion of the radiating elements in the array of radiating elements are surrounded by a plurality of spaced-apart parasitic elements, respectively, and at least a portion of the parasitic elements in the array of parasitic elements each comprise a first parasitic subcomponent extending in a first direction and a second parasitic subcomponent extending in a second direction perpendicular to the first direction. In addition, the present disclosure also relates to a base station antenna comprising the antenna assembly. This is capable of effectively improving the cross-polarization performance of the base station antenna and improving the radiation boundary of the base station antenna.