The current study set out to examine the effectiveness of focused written corrective feedback (WCF) on ESL learners’ writing accuracy; in particular, the grammatical accuracy. It targeted only one linguistic feature (i.e. English articles) using a pre- and post-tests. It compared the effects of focused feedback on writing accuracy with 30 ESL learners at a language program at Washington State University. One sample dependent t-test was used to compare the means of the pre- and post-tests using SPSS. As on group, all participants have had an intervention in which they were exposed to different kinds of writing, and received focused feedback on only definite and indefinite article errors. The results indicate that there was a significant difference between pre- and post-tests in writing accuracy. Participants significantly improved their use of articles during the intervention and, therefore, increased their writing accuracy. This study contributes to other studies in the literature that written feedback is effective, and gives more pedagogical credits to teachers providing WCF.