Based on a set of reference indicators, a tool was designed for the evaluation “ex post” of sustainability of units of managed natural forests in Costa Rica. This set was developed using a hierarchical structure of principles, criteria and indicators of sustainability. The resulting reference list consists of 5 principles, 12 criteria and 30 indicators, classified as essential by a group of experts in forest management in Costa Rica. The set of indicators allows studying the dimensions and attributes that delimit the sustainability of the ecosystems. The selection procedure and the likely contribution of this set to forest management addresses, firstly, the economic, social, ecosystemic and institutional conditions of Costa Rica. However, the set of indicators is useful for other regions of the world, previous adaptation of the threshold values to the local conditions of the ecosystem. Additionally, the ecosystemic dimension (productivity, stability, adaptability) is ratified as a condition of first order for the sustainability, but the experts reinforce the idea that the institutional dimension (equity and governance) is a challenge for the evaluation of sustainability.