This study assessed the readability of the four recommended physics textbooks in senior secondary schools in Osun State of Nigeria. A total of 25 physics teachers and 300 senior secondary three (SS3) physics students were randomly selected in the 12 secondary schools used for the study. A survey design was used for the study. Results showed that the four physics textbooks were appropriate for secondary school students in Osun state of Nigeria in terms of age (Fry graph mean age = 17 years, students' mean age =15 years). The books had the highest rating by students on illustrations and clarity of prints while the lowest ratings were on sentence structure and examples. Teachers considered the vocabulary as appropriate while the exercises were considered least appropriate. The study also showed that the four physics textbooks were adjudged readable in term of students' ability to read and understand the contents. However, senior secondary school physics textbooks (69%) was found to be most readable, seconded by ordinary level physics (64%), followed by principle of physics while science teacher association of Nigeria (STAN) physics (15%) was found to be least readable by the students. It is recommended that the readability of textbooks and the reading ability of students should be part of the criteria for selecting textbooks.