The construction industry generates large volumes of solid waste that, when poorly managed, degrade soil, pollute water bodies, obstruct drainage and threaten public health. This study assessed sustainable waste management practices among construction stakeholders in Osogbo, Osun State, Nigeria, with a view to determining their implications for the local ecosystem. A descriptive survey research design was adopted, guided by four objectives: identifying the major waste types generated on site, examining current management practices, evaluating stakeholder awareness of sustainable practices, and assessing perceived ecosystem effects. Using the Krejcie and Morgan (1970) table for sample size determination, a structured questionnaire was administered to construction stakeholders in Osogbo and 108 valid responses were retrieved and analysed in SPSS using frequencies, percentages, mean, standard deviation and the Relative Importance Index (RII). The instrument returned excellent internal consistency (Cronbach's Alpha = 0.995). Findings show that masonry debris, packaging materials and finishing waste are the most prevalent waste types; component reuse and open dumping are the dominant management practices; awareness is strongest around practical storage and safety benefits but weaker around statutory regulation; and environmental health risk from open burning is the most keenly perceived ecosystem effect. The study concludes that construction waste management in Osogbo is characterised by a persistent gap between stakeholder awareness and actual site practice, sustained by cost-consciousness and weak enforcement rather than ignorance. Recommendations include phased material procurement, mandatory designated waste bays, stronger local enforcement of waste bye-laws, and cost-incentive schemes to close the awareness-practice gap and support Nigeria's green growth agenda.