This paper broadly addresses the question of whether university students whose major does not require expertise in logic can improve their ability in deductive reasoning by taking an introductory course in logic. In particular, our study aims to evaluate a course in deductive logic offered by one of the authors in a department of elementary education. Two experiments were conducted by using a pretest-posttest design with an experimental and a control group as well as a follow-up test after 6 months on the experimental group. The results of the analyses showed that the course mainly succeeded in strengthening students' general logical ability in the experimental group and these gains were retained 6 months later in the follow-up test. Promises and constraints of the study are discussed in the educational context.