The ongoing debates about the effects of human population growth (HPG) is one of the concepts in education for sustainable development (ESD). Beliefs toward HPG are an important construct for teacher education because beliefs potentially interfere with their instructional practices and students' beliefs, attitudes and behaviors. Accordingly, this study focused on developing and validating an instrument to explore pre-service teachers' beliefs toward the effects of HPG. The instrument was piloted, revised, and the main study was administered to 658 pre-service teachers. The instrument revealed five dimensions: requirements to support HPG; neo-Malthusian environmentalism; population and national economy; quality of human life; and population, resources and environment. Pre-service teachers' beliefs revealed that they needed additional support to understand multiple and nested interactions among HPG, urbanization, energy demand and national economy within the context of sustainability. This instrument is a promising tool to provide insights when designing courses on ESD for pre-service teachers.