Metacognition and critical thinking have become essential variables in science teaching. However, the low level of metacognition and critical thinking of students at various levels of education in Indonesia is still widely reported. Therefore, to minimize the gap that occurs, an instructional model is needed as an alternative solution, namely the GIRQA instructional model. This study aims to determine the effect of implementing GIRQA on the students' metacognition awareness and critical thinking skills in Biology. This quasi-experimental study used a non-randomized control-group pre-test and post-test design. The populations were 214 students from the 10th grade of the science program in one of the senior high schools in Jombang Regency, East Java, Indonesia. We used a cluster random sampling design to assign two groups (72 students) as the research samples. The instrument for measuring metacognition awareness was the metacognition awareness inventory. Then, an integrated essay test measuring critical thinking skills was given. The results showed differences in metacognition awareness and critical thinking skills between students taught with the GIRQA instructional and traditional learning models. The post-test mean of students' metacognition awareness and critical thinking in the GIRQA group was superior to the traditional group. GIRQA contributed 48.1% to students' metacognition awareness and 41.4% to students' critical thinking skills. Future research shall explore the relationship between metacognition and critical thinking using several instructional models.