Climate variability, sea‑level rise, and rapid land‑use change increasingly exceed the design capacity of ageing drainage and irrigation (D&I) infrastructure in Guyana, heightening risks of pluvial and coastal flooding, drought stress, and salt‑water intrusion. This study evaluates how Nature‑based Solutions (NbS) can augment and de‑risk existing grey assets, drawing on global best practice and Guyana‑specific evidence to inform the National Drainage and Irrigation Authority’s (NDIA) strategic planning. The study seeks to (i) identify fit‑for‑purpose NbS and green–grey hybrids for priority D&I contexts, (ii) synthesize relevant international and regional best practices to derive design and implementation lessons for Guyana, (iii) assess performance and trade‑offs of select NbS interventions, and (iv) propose a practical roadmap, monitoring framework, and financing options for scaled adoption.