The present study aimed to explore the effect of an Informal Digital Learning of English (IDLE)-based program on developing incidental vocabulary learning and vocabulary learning motivation among secondary stage EFL students. The study used the pre-posttest quasi-experimental one group design. Forty first year secondary stage EFL students participated in the present study. The participants practiced autonomous informal learning activities in out-of-class digital environments. The instruments of the present study included an EFL vocabulary test and a vocabulary learning motivation questionnaire. Data were treated statistically using SPSS. Results of the study showed that the IDLE-based program was found to be effective in developing incidental vocabulary learning and vocabulary learning motivation among secondary stage EFL students.