We developed a free will and determinism scale in Japanese (FAD-J) to assess lay beliefs in free will, scientific determinism, fatalistic determinism, and unpredictability. In Study 1, we translated a free will and determinism scale (FAD-Plus) into Japanese and verified its reliability and validity. In Study 2, we examined the relationship between the FAD-J and eight other scales. Results suggested that lay beliefs in free will and determinism were related to self-regulation, critical thinking, other-oriented empathy, self-esteem, and regret and maximization in decision makings. We discuss the usefulness of the FAD-J for studying the psychological functions of lay beliefs in free will and determinism.