The purpose of this study was to develop and validate a behavioral observation tool that evaluates college students communication competency in real-time, online learning situations (e.g.synchronous online classes). To this end, existing test tools related to communication competency were collected and analyzed to derive the dimensions of evaluation and evaluation elements. The dimensions of evaluation consisted of three categories: function, attitude, and skill. Evaluation elements in the functional dimension included self-expression of opinion, understanding of others opinions, and proceedings of opinions. Evaluation elements in the attitudinal dimension included activeness, respect for others, and openness; and the evaluation element in the technological dimension consisted of the technology element. A total of 23 behavioral indicators were developed, and the video data of 154 college students who participated in synchronous online classes were collected to apply and evaluate these indicators. Based on the developed behavioral indicators, 11 raters assessed the college students communication competency, and reliability between raters was calculated. Through the original scoring and reassessment processes, reliability among raters and internal consistency reliability for 23 behavioral indicators met the criteria for acceptance. The development of this measurement tool is meaningful in that it measures communication competency in online situations that have recently become more common, and it also measures communication competency based on behavioral indicators.