The current study aimed at investigating the impact of the social constructivist approach (SCA) via online learning environments on EFL students' critical writing skills. Sixty-four English major senior students were randomly chosen and assigned to an experimental group (n=32) and a control one (n=32). A pre-post critical writing test to assess students' level before and after the treatment, and semi-structured interviews to gather qualitative data were used as the study instruments. Findings indicated that using the SCA via online learning environments had a significant impact on the students' critical writing skills. Hence, curriculum designers and EFL instructors need to utilize the different features of the SCA, as well as incorporate various online learning tools, in order to enhance students' critical writing skills.