Practical work plays a vital role in science education by fostering inquiry, conceptual understanding, and learner engagement. However, in resource-limited contexts, teachers face persistent challenges in implementing effective hands-on learning. This study explored the barriers encountered by Grade 10–11 Biology teachers in the Ondobe Circuit, Ohangwena Region of Namibia, when preparing and conducting practical lessons. A qualitative case study design was employed. Four Biology teachers were purposively selected from nine schools offering the subject. Data were collected through classroom observations, semi-structured interviews, and document analysis, and analysed thematically using Bandura’s Social Cognitive Theory, particularly the Triadic Reciprocal Causation model. Results revealed multiple constraints, including inadequately equipped laboratories, scarcity of consumable materials, limited time for lesson preparation, and inconsistent safety practices. Many teachers relied on demonstration-based approaches, which reduced learner participation and skill development. Additionally, teachers exhibited gaps in pedagogical content knowledge, particularly in aligning practical activities with syllabus objectives and assessment standards. These challenges hinder learners’ mastery of practical competencies and contribute to weak examination performance. The study underscores the need for targeted professional development, improved laboratory resourcing, and sustained institutional support to enhance the quality of practical science instruction in schools.