To examine script effects, monoscriptal Spanish–English (SE) bilinguals, who use two similar Roman alphabetic systems, were compared to biscriptal Chinese–English (CE) bilinguals, who use logographs and Roman alphabets. On the Attention Network Test, script effects were most evident in global processing efficiency (i.e., inverse efficiency and reaction time) and in the local network of executive control in favor of biscriptal CE bilinguals over matched monoscriptal SE counterparts. Literacy effects were found on the executive control network among Chinese–English bilinguals of high L1-literacy skills over their script- and immersion-matched counterparts, who varied only in low L1 literacy. In a similar vein, results of the multiple regression analysis demonstrated that script and literacy are significant predictors of executive control capacities. Our results suggest that script variation in a bilingual's language pair is an important modulating factor that enhances overall attention efficiency.