This research aims to examine the relationship between high school students' reading habits and their smartphone addiction level. The sample consisted of 512 high school students studying in various private schools located in Turkish cities of Istanbul and Edirne. High school students were included in the study using the convenience sampling method. The study was conducted by using the correlational model of quantitative research methods such as descriptive statistics, independent samples t-test, one-way variance analysis, and Pearson correlation coefficient techniques. High school students' smartphone addiction level was found to be moderate, with 8.81 books being read by students over a year. When reading books, students were found to have quitted the reading practice 2.96 times on average. The analysis of the results showed that girls were more likely than boys to tend towards smartphone addiction. As far as the reading habits are concerned, the students who reported poor reading habits or did not read any book during the week, and the ones who expressed a distraction each time reading a book reported higher smartphone addiction levels. A significant positive relationship was found between smartphone addiction and the number of distractions while reading. Consequently, a significant negative relationship was found between the high school students' smartphone addiction level and their reading behaviours, and some recommendations were offered for practitioners and future researchers.