The current study aimed to assess the readability level of the 10th and 11th grade EFL students’ textbooks “Action Pack” in Jordan. The reading texts in both the 10th and 11th grade EFL students’ textbook were examined. There were 34 reading texts in the 10th grade student textbook and 30 in the 11th grade student textbook. 50% of the number of texts was selected for the study sample. The sample texts in both books were transferred to word document in order to use modern software (wordcounter.net) for analyzing the data in terms of word count, sentence count and syllable count. The instruments of the study were two formulas used for assessing readability of textbooks worldwide. These formulae are: Flesch reading Ease (FRE) formula, and Flesch – Kincaid grade level (FKRE) formula. The results showed that in terms of the FRE formula the 10th grade readability level was (64). And the 11th grade readability level was (61). Results also showed that according Flesch – Kincaid grade level formula the readability of the 10th grade EFL students’ textbook was (8) and the readability level of the 11th grade textbook was (9). These results show that the readability level of the 10th and 11th grade EFL students’ textbooks are below the intended level. The recommendations based on these findings is for course designers to revise the textbooks reading texts and to check them for readability prior to publication. (Keywords: Readability level, EFL textbooks, Readability formulas)