The case study-based module on chemical thermodynamics course (ideal and real gases) was developed to fulfill the needs of undergraduate students in online learning during the COVID-19 pandemic. The purpose of this study was to test feasibility of case study-based module. The case study-based module refers to the 4D model (define, design, develop, and disseminate) by integrating the one group pretest-posttest design at the develop stage. The feasibility of the module was measured through validity, practicality and effectiveness using validation sheet, evaluation test sheet and questionnaire sheet. Data were analyzed descriptively, quantitatively (Wilcoxon Signed Rank Test) and qualitatively. The case study-based module was suitable for one of learning tools, which was proven by the findings that (1) meets valid and reliable criteria, (2) meets practical criteria with support for general achievements students' very positive response to the aspects of module (construction, material, motivation and case study), and (3) meets the effective criteria by increasing the average score pretest-posttest in medium category which contains the cognitive level of analyze-C4, evaluate-C5, and create-C6. The implication of development case study-based module can facilitate students in online learning during the COVID-19 pandemic so that they will successfully reach the course learning outcomes of Chemical Thermodynamics, which includes mastery of knowledge about main principles of thermodynamics, ability to solve science and technology problems, ability to use information and communication technology based learning resources, make decisions based on the relationship of concepts with laboratory activities, and practice responsibility.