This action research aims to investigate the effectiveness of a Slow Reading method in improving English basic literacy and the affective attitudes of one elementary school English underachiever. Based on the literature review and an analysis of the school program, a Slow Reading method was developed. As the result of the first action carried out to the underachiever, his reading skills and participation were improved. But with the difficulties of phonemic awareness and reading the alphabet, the underachiever had still difficulty in reading and learning anxiety. Through interaction between the English teacher, the researcher, and the student, the Slow Reading method was modified to focus on phonics instruction and various slow reading strategies. As the result of the second action, the underachiever improved his cognitive reading abilities (alphabet recognition, phonemic awareness, reading and writing ability, and word association ability), and affective attitudes(motivation, interest, and participation). In addition, his self-directed learning ability of using his own strategy in dealing with some tasks has appeared.