The study examines the effect of explicit form focus instruction and specifically metalinguistic information feedback on the development of both implicit and explicit knowledge of adult English as a Second Language (ESL) learners. Ninety-one subjects at the lower intermediate level were carefully selected through placement test at one of the selected education centre in Kuala Lumpur and randomly assigned into experimental and control groups by the researcher. A quantitative study was conducted over approximately four weeks in 16 sessions. Modal (can and have to), past tense with -ed, Present perfect (since and for), Comparatives, Unreal conditionals were chosen as the target structures. Target structures were taught based on the lesson plan of the study. Pretest and posttest were given before and after the intervention program. The tests consisted of two tests designed to measure implicit knowledge (i.e., EOIT & TGJT) and two other tests (i.e., UGJT & MKT) to measure explicit knowledge. Results of ANCOVA analysis show gains on both types of knowledge on the posttest. The theoretical implication of the results suggests explicit instruction adequately facilitates development of L2 implicit and explicit knowledge. Pedagogically, these results suggest that explicit instruction on some English language features may benefit L2 learners, especially in facilitating their implicit knowledge.