The purpose of this research is to determine the use of argumentation education model as a specific topic in differentiation-enrichment of instructional environments in the development of critical thinking of gifted students in forensic chemistry activities. The research was conducted on a qualitative research design based on a case study with eight gifted students in 2017-2018 educational year in an institution that provides education to gifted individuals in Ankara. As data collection tools, worksheets of teaching sequence making the gifted students reconstruct each of the forensic chemistry activities as arguments and participant observer’s observation notes were used. During the data collection process, the gifted students carried out each forensic chemistry activities by following each other’s thinking strategies, and then they reconstructed these activities with individual argumentation. Data were analyzed via content analysis and descriptions. As a result of the research, it was found that the gifted students could reconstruct forensic chemistry activities as arguments and that thanks to these activities their critical thinking developed as well. In addition, an exemplary model is presented for the instructors of gifted students at the end of the research with this differentiation-enrichment application integrated with forensic chemistry-argumentation-critical thinking.