Detailed knowledge of learners’ relationships is very important for successful teacher pedagogical work in a classroom. The familiarity with the relationships is important, especially in the case of teenagers’ class. All teachers should deal with the problem of learners that are out of their classmates’ interest (so called isolated learners or isolates) in such class and think about possibilities to integrate them into the class. Natural idea how to do it is that of using some non-traditional learning methods, especially the methods based on working in small groups involving learners’ cooperation. Problem-based learning (PBL) as one of these methods with an influence on learners’ relationships was a subject of the further described research. Within PBL courses, students work with classmates to solve complex and authentic problems that help develop content knowledge as well as problem-solving, reasoning, communication, and self-assessment skills. The aim of the research was to answer the question: Can the problem-based learning help to integrate isolated learners into the class? The research was realized as a pretest-posttest design for the sample of 182 learners of seventh, eighth and ninth grades of basic school. Standardized sociometric questionnaire B-3 was used to determine the number of isolated learners before and after using the problem-based learning. Consequently, using the Wilcoxon statistic test of significance, the hypothesis was verified that the number of isolates after the problem-based learning is statistically significantly lower than that of the case before using the non-traditional learning method. Accordingly, the research results justify implementation PBL into education.