This article reports on an 8-week study that investigated the differential effects of two written corrective feedback (CF) options on 92 low-intermediate EFL students' explicit and implicit knowledge of English articles and the extent to which language analytic ability might influence the effect of written CF. The study used a pretest-treatment-posttest-delayed posttest design with three groups: a direct-only correction (DOC) group, a direct metalinguistic correction (DMC) group, and a control group. The acquisition of explicit knowledge was measured by an error correction test, and implicit knowledge was measured by a picture-cued writing test. It was found that both the DOC and the DMC benefited explicit and implicit knowledge, but no significant differences were reported in their effects on each type of knowledge. This study also showed that language analytic ability mediated the effectiveness of the DOC rather than that of the DMC. These findings are discussed from the perspective of cognitive psychology and implications and suggestions for further research are put forward.