Previous priming studies suggest that, even for bilinguals of languages with different scripts, non-selective lexical activation arises. This lexical decision eye-tracking study examined contributions of frequency, phonology, and meaning of L1 Japanese words on L2 English word lexical decision processes, using mixed-effects regression modeling. The response times and eye fixation durations of late bilinguals were co-determined by L1 Japanese word frequency and cross-language phonological and semantic similarities, but not by a dichotomous factor encoding cognate status. These effects were not observed for native monolingual readers and were confirmed to be genuine bilingual effects. The results are discussed based on the Bilingual Interactive Activation model (BIA+, Dijkstra & Van Heuven, 2002) under the straightforward assumption that English letter units do not project onto Japanese word units.