The purpose of this study is to examine the relative effects of two online peer assessment roles (assessor and assessee) on students' performances in problem-solving. The participants included 70 students enrolled in the Special Teaching Methods II course, offered during the 2013-2014 spring semester. Participants engaged in a number of learning activities in an online learning environment during the six-week intervention process. Results indicated that both assessors and assessees improved their problem-solving skills. Additionally, assessors, compared to assessees performed better on justifying their problem-solving with sound reasoning. (C) 2015 Elsevier Ltd. All rights reserved.