Abstract This research was aimed to develop a valid and practical Students’ Worksheet of Natural Science for junior high school students based on critical thinking skills. The development model used in this research was the Rowntree development model consisting of three steps, namely planning, development, and evaluation. The evaluation step was the formative evaluation step by Tessmer consisted of five steps, namely self-evaluation, expert review, one-to-one evaluation, small-group evaluation, and field testing. However, the field testing step was not done because the research objectives were only focused on validity and practicality. The data had been collected using walkthrough and questionnaire techniques. The results showed that the developed product was in a highly valid category based on the score of expert validations. The validation score obtained from the language expert was 4.73, the score obtained from the design expert was 4.56, and the validation score of critical thinking skills was 4.56. At the one-to-one evaluation step, the product was declared as very practical, practical, and quite practical. At the small-group evaluation step, the product was declared very practical and practical. Thus, the developed product has been valid and practical.