A recent approach to second language (L2) instruction is integrating Form-Focused Instruction (FFI) in a L2 classroom. One way to achieve this is through incidental focus on form (FonF) which draws learners‟ attention to linguistic items as they arise. Focus on form has been theorized as benefitting to the L2 learners, but few empirical investigations have been done in English for Speakers of Other Languages (ESOL) provision in this regard. This study looked into the effects of FFI and tried to compare the two types of FFI (implicit and explicit) and further investigated which type of instruction helped to promote L2 language development. To carry out this research „The Effects of Form-Focused Instruction on ESOL Learners‟ Accuracy of Written Production‟, 45 experienced teachers at various ESOL centers in the UK and 16 ESOL learners in Entry level 2 or B1/B2 level at the „Skills for Life‟ Centre in Preston College, UK, who were as the experimental group of this study. The ESOL teachers‟ perception about the effectiveness of FFI in the L2 classroom was yielded through questionnaires and one to one interviews. The experimental study was conducted by individualized tests for the ESOL learners in which productive tests were designed to induce their progressive written production and time triangulated data. The results revealed that planned focus on forms (FonFs) is preferred and practiced by the ESOL teachers in their L2 classrooms and seen as beneficial. The results of the tests showed that learners were able to recall correctly or partially correctly the intended linguistic items. This suggests that explicit FFI may be of some benefit to the ESOL learners, particularly if they are encouraged to incorporate the targeted linguistic items into their own L2 production.