This study aims to develop a valid and practical character value assessment instrument for elementary schools. The instrument developed was in the form of an observation guide which consists of 78 items and is based on the five main values of the National Character (Religious, Communal Work, Nationalist, Independent, and Integrity) and the competence of grade IV elementary school subjects. The assessment instrument was developed using the ADDIE model: (1) Analyze, (2) Design, (3) Develop; (4) Implement; and ( 5) Evaluation. This study involved experts and linguists on character education as well as practitioners or elementary school teachers. The research instrument used was a validation questionnaire for character education experts and linguists as well as practitioners (teachers) and a product practicality questionnaire for teachers. The data obtained in the form of validation data from character education experts and evaluation experts as well as linguists and teachers as practitioners. Finally, it is concluded that the development of the instrument on students' character value assessment resulted in 74 final product items that were categorized as valid and practical. Thus, the product is suitable to use as an assessment tool for students' character value at grade IV elementary school.