Mathematical proof, often regarded as the heart of mathematics, is essential for interconnected mathematical knowledge. However, proof-writing skills do not develop inherently. Effective learning environments are vital for university students to enhance these skills. This study investigates the impact of the ISMAT model on pre-service teachers' proof-writing skills. The model, based on quasi-experimental paradigms and arguments from Popper (1979) and Lakatos (1961, 1976), utilizes dynamic geometry software to enhance the understanding of proof functions. It is hypothesized that a social learning environment, augmented by dynamic geometry, will yield observable effects. The research employed a quasi-experimental design with experimental and control groups of pre-service mathematics teachers. The experimental group received 14 weeks of Euclidean geometry lessons using the ISMAT model, while the control group followed traditional methods. Data were collected through proof-writing tests administered pre- and postinstruction. The evaluations were conducted using Senk's (1983) framework for assessing proofwriting skills. Results indicated that the ISMAT model significantly enhanced proof-writing skills compared to traditional teaching methods. Such approaches are recommended to foster active student engagement in the proving process.