This article describes a pilot study investigating the effects of 5W1H writing activity on students' English texts. Specifically, the author examined whether the writing activity focusing on questioning the 5Ws and 1H improves clarity in the revisions of students’ papers. The participants of this study were 14 sophomores at a large private university in western Japan. The students were provided with 5W1H worksheets in which the key considerations for the activity were summarized. Students conducted the activity in a pair or a group setting over six classes in total. To evaluate the process, the author and one independent rater assessed students’ texts before and after the process, using a writing rubric evaluating text clarity. Also, students’ pre- and post-texts were carefully examined to identify their achievements through the process. The scoring comparison of the pre- and post-texts showed a positive influence of the treatment. Text examination showed that the revisions leading to a better text became clearer with modified 5W1H details. The activity refocused students’ attention on the importance of clearly describing required 5W1H aspects of information. Thus, the author concluded that 5W1H writing activity enhanced students’ writing performance.