The study investigated teachers' knowledge of reading comprehension processes and reading comprehension instruction. The study was carried out among teachers (N = 65) in Estonia. The content analysis classified qualitative data from semi-structured interviews as quantitative data. The results showed that teachers' content knowledge about reading comprehension processes and pedagogical knowledge of reading comprehension instruction were considerably variable yet mostly limited. Special education teachers (n = 37) mentioned a wider range of reading strategies than classroom teachers (n = 28). When describing how to support struggling readers, significant differences emerged between the teacher groups: Special education teachers mentioned activities to support students' reading comprehension more frequently than classroom teachers whereas classroom teachers mentioned activities for supporting reading motivation more often than special education teachers. Teachers' lack of knowledge about reading comprehension processes and reading comprehension instruction indicate the need to improve these topics in preservice and in-service teacher training to enhance their teaching skills.