This study reveals the reduction of uncertainty in the interpersonal relations of Batak and Javanese students in Yogyakarta. The character differences between the Batak and Javanese people are strongly influenced by language, culture, and habits. The Batak people have a violent character, are temperamental, rude, and speak at a loud volume. In addition, they also have a character that is firm, honest, open, and does not beat around the bush. As for the Javanese, they have a character that upholds the philosophy that a person's self-esteem depends on speech and language so everyone must take care of what they say. The theory used in this study is uncertainty reduction from Berger and Calabrese. This study used descriptive qualitative methods, with data collection techniques through in-depth interviews, informants were determined using purposive sampling techniques, validity testing used source triangulation, and data were analyzed through several stages, namely data collection, data reduction, data presentation, and concluding. The results of the data findings obtained an illustration that each pair of informants had a different process of reducing uncertainty. The pair of informants AW and KS is more significant in reducing uncertainty than the pair of informants LD and LF. Factors that influence the significance include the existence of socialization skills and the number of meetings between LD and LF, gender equality, and experience similarities between AW and KS.