Extensive reading with graded readers has been proved to be an approach that helps learners improve their reading ability. However, only a few studies have explored the effects of additive extensive reading with other types of reading materials on struggling EFL learners. This study investigated the effects of Science and Research Association Reading Laboratory (SRA) and Reading Reflective Journals (RRJ) as additive extensive reading activities on struggling EFL tertiary students' English reading ability and performance. This study was a comparative mixed-methods approach conducted at a Thai university over 15 weeks. The students were two intact groups enrolled in a reading course taught by the researcher. One group was assigned to SRA, and the other to RRJ. Data were collected by means of English reading pre- and post-tests, students' reflective journals, and an open-ended questionnaire. Both quantitative and qualitative results indicate that SRA and RRJ positively impact students' reading ability, their attitudes towards English reading, and their knowledge. Since SRA and RRJ are based on different theories, each has its limitations. The combined activity of SRA and RRJ features is suggested. The factors affecting the use of additive extensive reading (ER) should also be considered when implementing any type of ER.