As western society becomes increasingly reliant on scientific information to make decisions, citizens must be equipped to understand how scientific arguments are constructed. In order to do this, pre-service teachers must be prepared to foster students' abilities and understandings of scientific argumentation in the classroom. This study investigated how instruction in the Toulmin Argumentation Protocol (TAP) impacted pre-service science teachers' ability to write sound and logical scientific arguments. The study occurred in the context of a pre-service methods class on the socio-scientific realm of secondary science education at a university in the USA. Through the use of quantitative methods, investigation findings indicate that there was a positive impact on pre-service science teachers' ability to construct sound scientific arguments through instruction in the TAP within the one semester course where this research took place. (Contains 4 tables and 2 figures.)