Research has shown that language and literacy skills in a first language (L1) are related to performance in a second language (L2) and that these relations are reciprocal. However, cross-linguistic skills related to word reading are influenced by numerous factors. These include linguistic factors such as the specific language and literacy skills being examined and the languages being compared. They also include societal/contextual factors, such as the linguistic and educational contexts where learners reside. Specifically, contextual factors include the use of the L1 and L2 in the curriculum (e.g., immersion, dual language, heritage language, available supports), teaching methods, and whether the L1 and L2 are societal languages. Research based on the science of reading for bilinguals has shown that phonological awareness is highly related across languages, whereas other language skills have shown differential levels of relations to reading. Word-reading skills are also related, but these relations are more complex and are due to linguistic factors such as script and linguistic typology and societal/contextual factors, such as instruction and exposure to each language, which are consistent with various theories. Consideration of a wider range of L1s and L2s and specific contextual/societal factors should be included more systematically. Additionally, learner experiences and specific L1 and L2 variables should be considered in educational decisions.