This study examined the effects of an intervention using audiobooks for the development of reading fluency, in terms of reading speed, reading comprehension, and motivation to read among Kazakhstani English as a foreign language (EFL) ninth-grade learners in the K-11 system. Silent reading with audiobooks (experimental group) and silent reading only (control group) were compared with a mixed-method study design, a reading motivation questionnaire, and a semi-structured interview. Quantitative data analysis was conducted using analysis of covariance (ANCOVA). The experimental group was found to significantly outperform the control group in reading speed while preserving substantial comprehension of the texts. The results further revealed that, while both groups' motivation level increased, no statistically significant difference was found between the experimental and control groups, suggesting that the use of audiobooks was not superior to silent reading for motivation enhancement. Nevertheless, a qualitative analysis of data obtained from the interviews revealed that the use of audiobooks had an overall positive effect on students' attitudes toward the use of audiobooks and reading comprehension. The study concludes with a discussion of limitations and suggestions for future research.