This study investigated the impact of peer review on developing pre-service science teachers' (PSTs) written arguments about socioscientific issues related to chemistry. In the study, a quasi-experimental design was used with experimental (32 PSTs) and comparison class (33 PSTs). The participants were PSTs who were juniors in a public university in Turkey. Argumentation procedure for each group was conducted by the same instructor identically except peer review of written arguments in the experimental class. Toulmin's (1958) argument pattern was used for coding the arguments, and argumentation levels were determined by the levels proposed by Venville and Dawson (2010). Results indicated that the experimental class generated more Level 3 and Level 4 argumentation comprises more complex arguments than the comparison class. In both groups, more complex arguments were generated in the contexts of the use of medicine and home chemicals whereas less complex arguments were generated in the context of chemical additives in food. The conclusions and implications for science educators and researchers were discussed.