Global loss of biodiversity has directly and indirectly been caused by human activities. Environmental Impact Assessment (EIA) attempts to address the loss of biodiversity caused by development projects, by avoiding, reducing or compensating the loss (in that order following the mitigation hierarchy approach). Evidence suggests that in practice the mitigation hierarchy is not always applied correctly, and that monitoring is frequently absent, or flawed, meaning that the success of the mitigation measures, and their associated biodiversity outcomes, remain unknown. However, there is no literature that has systematically examined the application of the mitigation hierarchy and assessed the effectiveness of associated monitoring in an EIA system. This study fills that gap using Chile as an example because of its high biodiversity setting, and ease of access to EIA-related data. The results indicate that the use of compensation measures exceeded what would be expected from correct implementation of the mitigation hierarchy, and that there was also some misclassification of the measures. Monitoring studies focused on inspecting implementation of mitigation measures rather than measuring biodiversity outcomes (meaning that mitigation effectiveness cannot be fully evaluated). Further, there was a focus on specific elements of ecosystems and lack of consideration for broader biodiversity implications. Thus, the findings raise some concerns over the ability of EIA to achieve its goals of zero net loss of biodiversity. We make suggestions to improve the mitigation and monitoring aspects of the EIA process in Chile and would suggest that the recommendations are likely to have wider relevance to other jurisdictions.