Greening the West (GTW) is a regional initiative aimed at increasing urban greening, particularly the number of trees, in Melbourne’s western suburbs. Western Melbourne typically has comparatively low socioeconomic and health metrics, coupled with a significant deficit in trees and quality green space. Therefore the GTW group was convened by City West Water in 2011, to bring together 23 member organisations to collaboratively address this greening shortfall, in order to support community wellbeing. This research has involved extensive consultation with GTW stakeholders in order to determine how GTW works, its challenges, factors for success, achievements, areas for improvement, future directions, and implications for other current initiatives. This paper is a summarised version of a detailed case study report which has been reviewed by a wide variety of organisations with an interest in GTW, including water and urban planning experts within the Victorian Government. This research has found that through creating a critical mass of urban greening advocates, and a sophisticated communications strategy, GTW has been able to accrue significant external funding which has resulted in noticeable changes to the form of Melbourne’s west, most notably the planting of one million trees. Additionally, the group has changed organisational cultures and priorities, and started dialogues with private developers, which are incrementally increasing the levels of urban greening across the region. This research concludes with a series of recommendations for the Victorian Government and other stakeholders.