The bilingual literature has shown a bilingual disadvantage in spoken language compared to monolinguals. This study first investigated how highly proficient Mandarin-English bilinguals retrieved verbs and nouns compared to monolingual English speakers in a picture-naming task. In order to explain why bilinguals are disadvantaged than monolinguals in language processing, this study examined if it was due to the frequency effect, which was predicted by the “weaker-links”, or if it was due to the translatability effect, as predicted by the cross language interference. Results captured a bilingual effect, a word category effect, and a smaller bilingual disadvantage for verbs than for nouns in lexical retrieval. The bilingual disadvantage could be explained by the “weaker-links” hypothesis, rather than the cross language interference. But the smaller bilingual verb disadvantage could be partially explained by the cross language interference hypothesis. Clinical implications and future research directions were discussed.