Now that more than half of the world's population lives in cities, improving urban resource cycles is crucial for sustainable urban development. Currently cities are highly dependent on external supplies of water, energy, nutrients, and other materials, while local possibilities of self-production of such resources are generally overlooked. This article describes a novel method, the urban harvest approach (UHA), its rationale, and the steps toward sustainable urban resource planning. The UHA is based on the urban metabolism concept. Herein, a city is regarded to have multiple potentials in the form of untapped primary and secondary (already used) resources that can be utilized. The UHA works on the principle that urban systems and their direct peri-urban surroundings can become self-sufficient by applying three strategies: minimizing demand, minimizing outputs, and multisourcing. An elaboration of the UHA for the resource “water” at the building scale is also presented in this article. A freestanding house in the Netherlands and a similar house in Australia were studied, with a focus on indoor consumption. Results showed a 40% demand reduction when water-saving technologies were implemented. In both cases, after demand minimization, local resources were sufficient to cover the demand by recycling grey water and harvesting rainwater. These findings confirm that a multimeasure implementation according to the three different strategies is needed to achieve sustainable urban water systems. The UHA helps to structure large influences of urban context on water and other resource cycles as an aid to urban planners and water managers in designing sustainable urban areas.