This study investigates the influence of landfill management practices on the release of polybrominated diphenyl ethers (PBDEs) from coastal landfills in Newfoundland, Canada. By comparing PBDE congener profiles in leachate from a modern landfill with advanced treatment systems and a legacy landfill with limited infrastructure, we demonstrate the critical role of modern waste management practices in mitigating PBDE contamination. Both sites showed PBDE contamination, but the legacy landfill exhibited greater variability in congener types and concentrations. BDE-47 emerged as the predominant congener at both sites, with episodic spikes at the legacy landfill reaching 14.39 ng/L, alongside the presence of congeners like BDE-77, BDE-100, and BDE-183. GIS analysis revealed PBDE dispersion into nearby surface waters, posing risks to marine ecosystems. Landfill operator surveys provided insights into operational challenges, including limited e-waste diversion, fire risks from batteries, and inadequate leachate treatment at the legacy site, contributing to its vulnerability. This study underscores the need for proactive PBDE management in coastal landfills. The adoption of modern landfill technologies and enhanced e-waste diversion programs is vital for reducing contamination and protecting marine environments. These findings highlight the importance of sustainable waste management practices in safeguarding coastal ecosystems.