The group opened up 500 metres of pathways in their local woods in Felin Fach near Caernarfon so wheelchair users could gain access.
The Guides cleared 3ha of invasive laurel and brambles before planting more than 400m of trees and hedges. They cleared a stream of debris, and laid a boardwalk for pond dipping.
The initiative was funded with a Better Woodlands for Wales grant from Forestry Commission Wales.
Their work was voted the best in Wales when they scooped the £250 winner’s prize in a woodland-improvement category in the Tidy Wales Awards, honouring people who improved local areas.
Barbara Anglezarke, Forestry Commission Wales woodlands for people policy and programme manager, said: "The group worked with others to make their woodland a welcoming, accessible and thriving place for everyone to enjoy."