This study investigated the relative effects of deductive and inductive form-focused instruction (FFI) on the acquisition of 4 non-generic definite article uses(cultural, situational, structural, and textual) as assessed by explicit and implicit outcome measures. The tests utilized to assess EFL learners' acquisition of definite article uses were timed and untimed grammaticality judgment tests. A pretest and two posttests were conducted immediately and four weeks after the instructional interventions. Durable effects of FFI on intermediate Iranian learners' acquisition were found for different uses of definite article. In particular, the present study found that deductive and inductive FFI positively facilitates the development of explicit and implicit knowledge of non-generic definite article, both immediately after the instruction and, marginally decreasing, over time. Moreover, the findings indicated different difficulty levels for the 4 uses of definite article, with cultural use being the most difficult one followed in the order by situational, structural, and textual uses. This study’s findings contribute to our understanding of the efficacy of deductive and inductive FFI on EFL learners’ controlled (explicit) and spontaneous (implicit) use of a non-salient language forms at intermediate stages of L2 acquisition.