The purpose of the present study was to design and validate a curriculum model for social studies at the lower secondary education level based on 21st-century skills. This research is developmental-applied in nature and exploratory mixed-method (qualitative and quantitative) based on its objectives. The statistical population for the interview phase included curriculum planning experts, specialized social studies teachers, and educational group leaders in social studies. The sample consisted of 16 individuals who were selected through purposive sampling based on inclusion and exclusion criteria for the interview. The sample size was determined according to data saturation. The statistical population for the questionnaire and model validation phase included curriculum planning experts, specialized social studies teachers, educational group leaders, and doctoral students in curriculum planning at universities in Tabriz, totaling 700 individuals. The sample comprised 244 participants selected using the convenience sampling method, with the number determined according to the Morgan table. To collect research data, three instruments were used: research synthesis, semi-structured interviews, and a questionnaire, all of which were confirmed to be valid and reliable. Data analysis was conducted using SPSS version 26 and PLS version 3. According to the research findings, the proposed curriculum model for social studies based on 21st-century skills consists of three main components, eleven subcomponents, and fifty-eight concepts. It can be confidently stated that all three components, eleven subcomponents, and fifty-eight concepts are sufficiently robust to be retained in the model. Therefore, the proposed model demonstrates an acceptable level of fit. Additionally, the results showed that the designed model possesses desirable internal consistency and reliability. It can be confidently asserted that the convergent validity of the model is confirmed, indicating that the designed curriculum model for social studies in lower secondary education based on 21st-century skills has satisfactory validity.