This study examines the relative role of collocations (and its sub-types) and the effect of sociolinguistic factors on the reading comprehension skills of 4th-grade primary school students learning Turkish as a second language (L2). For this purpose, this study recruits L1 and L2 students from Başakşehir, Beylikdüzü, Fatih, and Esenler districts of Istanbul. The researchers collected data using the Language and Social Background Questionnaire (LSBQ) and a Reading Comprehension Test. The data were analyzed using statistical analyses such as the Independent Samples T-Test and the Independent Samples One-Way Variance Analysis (ANOVA) in the SPSS 22.0 package program. The study concludes that L1 students are more successful than L2 students in reading comprehension test with collocations. In terms of sub-types of collocations, L2 students are more successful in “restricted collocations” compared to other types. While L2 students' reading comprehension skills and success across collocation types are affected by sex, the language used while watching TV/video, and having technological devices such as tablet and computer; comprehension scores are not affected by the number of siblings, socioeconomic level, the language spoken by father within the home, and reading regularly. This study will significantly contribute to researchers, teachers, and policy-makers who are working with immigrant L2 students.