For science learning to be successful, students must develop attitudes toward support future engagement with challenging social issues related to science. This is especially important for increasing participation of students from underrepresented populations. This study investigated how participation in inquiry-based biology laboratory classes affected students' attitudes toward science, focusing on deaf, hard-of-hearing, and hearing signing students in bilingual learning environments (i.e., taught in American Sign Language and English). Analysis of reflection assignments and interviews revealed that the majority of students developed positive attitudes toward science and scientific attitudes after participating in inquiry-based biology laboratory classes. Attitudinal growth appears to be driven by student value of laboratory activities, repeated direct engagement with scientific inquiry, and peer collaboration. Students perceived that hands-on experimentation involving peer collaboration and a positive, welcoming learning environment were key features of inquiry-based laboratories, affording attitudinal growth. Students who did not perceive biology as useful for their majors, careers, or lives did not develop positive attitudes. Students highlighted the importance of the climate of the learning environment for encouraging student contribution and noted both the benefits and pitfalls of teamwork. Informed by students' characterizations of their learning experiences, recommendations are made for inquiry-based learning in college biology.