Can international judges be relieved of the duty to resolve disputes impartially? If not, what are the sources of their bias? Whereas the impartiality of international judges is an essential issue for the international rule of law, do factors affecting judicial bias actually exist? This article explores the conditions which might impinge the partiality of international judges. In this article I focus on practical aspects of judicial impartiality, analyzing the motives which affect the biased acts of international judges. I have divided the factors influencing judicial impartiality into five groups, depending on their origins: factors connected with judge’s activity, factors connected with judge’s identity, factors connected with geopolitical situation, economical-political factors and factors arising from procedural provisions of each tribunal. In this work I will be analyzing the first two groups of factors influencing judicial impartiality. This article seeks to make a contribution to outlining these factors on the basis of applicable law, existing case law and best practices. My observations are also related to sociological and psychological aspects which can influence the behaviour of a judge in the process of giving rulings in an international tribunal.