Summary: The present study aimed to investigate the cross-linguistic effect of L1 vocabulary, reading motivation and habits on L2 vocabulary, reading motivation and habits. In this respect, proposing a model, the study aims to contribute to foreign language education and research. The data was collected through vocabulary size tests, reading motivational scales, and reading habits questionnaires from 490 participants from four different state universities. The proposed model was analyzed with the PLSSEM technique as the complex theoretical model suggested. The results revealed that L1 vocabulary size and reading efficacy were the two predictors of L2 vocabulary size; however, L1 vocabulary size was the best predictor. Whereas L1 reading habits explained L1 vocabulary size, L2 reading habits did not predict L2 vocabulary size. Although participants' most highly endorsed reading motivational dispositions in L1 and L2 differed, only intrinsic reading motivation explained reading habits in L1 and L2. Moreover, L1 reading motivation and habits statistically significantly predicted L2 reading motivation and habits. In this respect, the study suggests that L1 vocabulary size and reading habits are essential in developing L2 vocabulary size and reading habits.