We used eye movement measures of paragraph reading to examine whether two consequences of bilingualism, namely, reduced lexical entrenchment (i.e., reduced lexical quality and accessibility arising from less absolute language experience) and cross-language activation (i.e., simultaneous co-activation of target- and non-target-language lexical representations) interact during word processing in bilingual younger and older adults. Specifically, we focused on the interaction between word frequency (a predictor of lexical entrenchment) and cross-language neighborhood density (a predictor of cross-language activation) during first- and second-language reading. Across both languages and both age groups, greater cross-language (and within-language) neighborhood density facilitated word processing, indexed by smaller word frequency effects. Moreover, word frequency effects and, to a lesser extent, cross-language neighborhood density effects were larger in older versus younger adults, potentially reflecting age-related changes in lexical accessibility and cognitive control. Thus, lexical entrenchment and cross-language activation multiplicatively influence bilingual word processing across the adult lifespan.