The complexity and fragmented nature and the multiple stakeholders in the construction industry often make it difficult to come up with a firm decision regarding sustainable building materials selection. The wrong choice could negatively impact the project objective and performance outcome. This study assessed the critical factor influencing the choice of sustainable building materials (SBM) selection on construction projects in the Southeast geopolitical zone of Nigeria. Data were collected using a well-structured questionnaire, nonprobability (purposive and snowball) sampling techniques, and an internet-mediated survey. Data analyses were carried out using the appropriate descriptive and inferential statistical tools and exploratory factor analysis (EFA). The study revealed recycled plastic, natural clay and mud, stone, bricks and tile, cellulose, stray bales, grasses, limestone, and wood timber, are the commonly used sustainable building materials. Also, their level of awareness is high while their adoption is moderate. EFA revealed that the major clusters of determinants of the choice of green building materials are: emissions minimisation, low running cost and reusability, low thermal and energy consumption efficiency, low cost and high health and safety consideration and waste minimisation. The key factors influencing the choice of sustainable building materials selection in construction are: reducing greenhouse gas emissions from buildings, materially embodied energy cost, operating and maintenance costs, non-toxic or low toxic emissions generated by the products/materials, recyclability of the building materials, availability of the technical skills, renewable (reusable) properties, inhibiting the impact of buildings on the environment, safety and health of the occupants, and appearance and aesthetic. It is recommended that consideration be given to these factors in selecting sustainable/green building materials in the designs and specifications of construction projects.