This study aims to compare the effectiveness of case-based instruction over traditional instruction in improving 11th grade students' understanding of electrochemistry concepts, attitudes toward chemistry, chemistry self-efficacy beliefs, and motivation to learn chemistry. In total, 113 students (47 males and 66 females) from three high schools participated in this study. Two of the classes from each school were randomly assigned to be either the experimental or control group. The experimental group was instructed by case-based instruction while the control group was taught by traditionally designed instruction. The Electrochemistry Concept Test, Attitude toward Chemistry Scale, High School Chemistry Self-efficacy Scale, and Chemistry Motivation Questionnaire were applied as pre- and post-tests to students in both groups. Moreover, a feedback form was administered to students in the experimental group at the end of the study to get students' opinions about the case-based instruction. One-way Multivariate Analysis of Variance (MANOVA) revealed that case-based instruction was an effective method to improve students' understanding of electrochemistry concepts, attitude toward chemistry, and intrinsic motivation to learn chemistry. The qualitative data gathered from the feedback forms also supported the results of the inferential statistics. Students reported that chemistry lessons were more interesting and enjoyable via case-based instruction.