Letter knowledge is one of the key components of literacy skills and a predictor of academic success. The present study explores how letter knowledge of preschool children is related to their language group (bilingual vs. monolingual) and socioeconomic status (SES) (mid-high vs. low). Forty-six monolingual Hebrew and 48 bilingual Russian-Hebrew children with a mean age of 5.8 years from mid-high and low SES backgrounds performed a set of Hebrew letter knowledge tasks that differed in their degree of complexity (letter discrimination, letter recognition out of symbols and letter naming). The results demonstrate that language group and SES are important predictors of letter knowledge performance on the higher complexity task (letter naming) but have no impact on performance on the lower complexity tasks (letter discrimination and letter recognition out of symbols). The discussion will focus on the employment of different levels of letter knowledge tasks with respect to children's language group and SES.