Determination of students' attitudes towards online cooperative learning is an important issue, which has not been studied adequately. In the literature, there are few scales to measure the attitude towards online cooperative learning for which validity and reliability have been proven. The main purpose of this study is to develop an attitude scale in order to specify students' attitudes towards online cooperative learning. The sample group is composed of 599 students for the first application and 242 students for the second. In order to detect the validity of the scale, exploratory and confirmatory factor analyses, item factor total correlations, corrected correlations and item discriminations were conducted. In order to assess the reliability of the scale, the level of internal consistency and the stability levels were calculated. OCLAS is a five-point Likert-type scale and includes 17 items that can be gathered under 2 factors. The analyses provided evidence that the Online Cooperative Learning Attitude Scale (OCLAS) is a valid and reliable scale that can be used in order to determine students' attitudes towards cooperative learning in online environments. (Contains 1 figure and 6 tables.)