This study aims to investigate the influence of Indonesian instructional books with a scientific approach on students' learning outcomes in scientific writing viewed from their academic ability. This is quasi-experimental research design. Techniques used to collect data were tests in form of multiple choice and essay, observations, and documentations. Before conducting t-test, the researchers conducted a prerequisite test. Its results for the influence of Indonesian instructional books with a scientific approach on students' learning outcomes showed significance values of 0.314 in cognitive domain, 0.032 in psychomotor domain, and 0.038 in affective domain. The results for the influence of academic ability on learning outcomes showed significance values of 0.065 in cognitive domain, 0.969 in psychomotor domain, and 0.528 in affective domain. The results for the interactions between of Indonesian instructional books with a scientific approach on students' and academic ability on cognitive, psychomotor. The conclusions of this study are: 1) Indonesian instructional books with a scientific approach influences students' learning outcomes in form of psychomotor and affective domains; 2) the academic skill does not influence students' learning outcomes in scientific writing, and 3) the interactions between Indonesian instructional books with scientific approach and academic ability have no effect on students' learning outcomes in scientific writing. It is recommended that Indonesian instructional books with a scientific approach can be developed to measure higher order thinking skills.