This study developed a Self-Regulated Second Language Self-Study Questionnaire that addresses the self-regulated learning (SRL) skills of learners of English as a foreign language in a self-study setting. Much attention has been paid to SRL in second language acquisition; however, contexts outside school have hardly been explored. To address this issue, based on the Motivated Strategies for Learning Questionnaire, a new questionnaire was created and applied to a sample of 112 Japanese university students. The exploratory factor analyses extracted three factors (i.e., self-efficacy, learner values, and test anxiety) from the motivation section of the questionnaire. Additionally, four factors (i.e., metacognitive strategies, problem solving, learning maintenance, and learning effort) were extracted from the learning strategy section. All seven factors showed adequate internal reliability. Additional confirmatory factor analyses demonstrated sufficient model fit indices for construct validity, whereas some were disputable.