Critical thinking skills are among the essential twenty-first-century competencies that need to be developed in biology learning. However, students’ critical thinking abilities are affected by various factors, including learning interest. This study aims to analyze the correlation between learning interest and students’ critical thinking abilities in Biology learning. This study used a descriptive correlational approach with a sample of 27 eleventh-grade students at SMA Negeri 1 Jetis, selected via random sampling. The research instruments consisted of a learning interest questionnaire with 19 Likert-scale statements and an essay test of critical thinking abilities comprising 10 questions developed based on critical thinking indicators by Ennis. The data were analyzed using the Spearman correlation test. The study found a positive and significant correlation between learning interest and students’ critical thinking abilities (r = 0.507, p < 0.05), indicating a moderate correlation. These findings indicate that the greater the students’ learning interest, the higher their critical thinking abilities. Thus, learning interest is one factor that supports the development of students’ critical thinking abilities in Biology.