There have been plenty of research studies which have demonstrated the efficacy of focus on form (FonF) approach in language teaching. However, processing instruction as a kind of FonF approach has not been given due attention. As such, the present study is an attempt to shed more lights upon the effects of the processing instruction (PI) on EFL (English as a Foreign Language) learners' acquisition of passive voice by comparing PI to dictogloss and an output instruction. The participants recruited for the study were 51 pre-intermediate level EFL students. The pretest revealed that there was no significant difference between the groups regarding passive voice knowledge. As to the treatment, the first group (n=17) received processing instruction, the second group (n=17) was exposed to dictogloss tasks, and the third (n=17) was given meaningful output instruction. In the immediate posttest, two types of tasks (interpretation and production) were used to assess the participants' English passive voice comprehension and production. The findings indicated that the processing instruction group outperformed dictogloss and meaningful output instruction in both tasks, and thus it had a significantly positive effect on the comprehension and production of the English passive voice.