This paper aimed to explore the impact of Kosovar teachers’ characteristics on the performance of fourth-grade students in TIMSS 2019. The paper addressed the characteristics of teachers, demographic, and academics, which are closely related to the overall performance of students. In this research, data from the TIMSS 2019 database were used, for which 4435 Kosovar students were tested, and 192 teachers were surveyed. The findings show that Kosovar students did not perform well in TIMSS 2019. They achieved 444 points in the field of mathematics and 413 points in science (average TIMSS 500 points) and were ranked 49th out of 56 countries participating in the test. Data from the teacher survey show that the characteristics of teachers, such as age, professional development, pre-service education, contemporary approach to teaching, etc., also played an important role in the low-scoring performance of Kosovar students in TIMSS 2019. Students who had a teacher with an average age of 30–60 years had a better performance on the test, achieving a difference of 20 points more, compared to students who had new or older teachers (under 30 years and over 60 years). The lack of professional development of teachers also had a major impact on student performance. On average, 25% of teachers in the last 2 years had attended training in certain areas, while on average 80% of them were willing to attend training programs that would improve the profile of their competencies.