This study evaluated the impact of two metalinguistic factors, English derivational awareness and English-Spanish cognate awareness, and the impact of two sociocultural factors, maternal education and children's length of residence in Canada, on English Language Learners (ELLs)' vocabulary knowledge. The participants of the study were 89 Spanish-speaking ELLs, 77 Chinese-speaking ELLs, and a comparison group of 78 monolingual English-speaking children in Grades 4 and 7. The sample included both first-generation (born outside of Canada) and second generation (born in Canada) immigrant children. The study yielded several important findings. First, it confirmed the strong link between derivational awareness and vocabulary knowledge observed in the previous research, and extended this relationship to two groups of ELLs from different first language backgrounds. Second, this study unveiled differences in vocabulary learning between Spanish-speaking and Chinese-speaking ELLs. While Spanish-speaking children were able to utilize the cognate strategy to learn English words, this strategy was not available for Chinese-speaking ELLs. With respect to the sociocultural factors, length of residence in Canada was significantly related to ELLs' vocabulary development. Interestingly, length of residence in Canada only influenced the development of noncognate vocabulary, but not cognate vocabulary, in Spanish-speaking ELLs, which provides additional evidence for these children's use of the cognate strategy. Finally, maternal education was not related to English vocabulary development. The theoretical and educational implications of these findings were discussed.