Multiple choice questions (MCQs) are commonly used for assessing students, but medical teachers may lack training in writing them. MCQs often have imperfections called item-writing flaws (IWFs) that can affect students' results and impede objective evaluation of their knowledge. This study aimed to evaluate a guideline-based faculty development intervention on writing MCQs at Levels 1 and 2 of the Kirkpatrick Model. MCQs written by teachers prior and after the intervention were analyzed with the Shapiro-Wilk test, Student's t-test, and Wilcoxon signed-rank test as appropriate. In addition, the phenomenological approach was chosen to describe experiences of 10 teachers in semi-structured in-depth interviews. Results showed satisfaction of teachers with the document. They found it helpful in writing MCQs and noticed the requirement for another guidelines. They appreciated it for its briefness and clarity. The statistical analysis of the quality of MCQs before and after the intervention showed that the document contributed to a statistically significant reduction of IWFs. To conclude, our results showed that a guideline document on writing MCQs may serve as a well-received and effective faculty development intervention. The document may be used as a flexible, time-saving, and just-in-time learning method, fitting needs of medical teachers.