Objectives The study aimed to examine the related variables that predict reading comprehension at the end of the first grade. Specifically, it focused on the relationship between reading comprehension and word decoding, reading fluency, vocabulary and syntactic knowledge, as well as the relative contribution of these variables to reading comprehension. Methods Sixty-four first-grade children were participated at the end of the school year. All children had nonverbal intelligence scores of 80 or above. Test were conducted on passage reading comprehension, word decoding, passage reading fluency, expressive vocabulary, semantic relation, and sentence comprehension. Pearson correlation and multiple stepwise regression were used. Results The results showed reading comprehension was positively correlated with expressive vocabulary, semantic relation, and reading fluency. In the stepwise multiple regression analysis, semantic relation, sentence comprehension, expressive vocabulary and reading fluency (but not word decoding) significantly predicted reading comprehension. Conclusions The finding suggests that language abilities including vocabulary and syntactic knowledge play an crucial role of reading comprehension even in early stage of reading development. Furthermore, passage reading fluency, which involves accurate and automatic word recognition rather than just word decoding accuracy, is a critical factor in reading comprehension. In Hanguel, where word decoding accuracy is acquired early and rapidly, linguistic knowledge and reading fluency are considered important variables for assessment and intervention, even in early grades.