Early deafness is thought to affect low-level sensorimotor processing such as selective attention, whereas bilingualism is thought to be strongly associated with higher order cognitive processing such as attention switching under cognitive load. This study explores the effects of bimodal-bilingualism (in American Sign Language and written English) on attention switching, in order to contrast the roles of bilingual proficiency and age of acquisition in relation to cognitive flexibility among deaf adults. Results indicated a strong high-proficiency bilingual advantage in the higher order attention task. The level of proficiency in 2 languages appears to be the driving force for cognitive flexibility. However, additional data are needed to reach conclusive interpretation for the influence of age of second language acquisition on higher order attention-switching ability and associated cognitive flexibility.