The increased recognition of inter-relationships between the environmental and health effects of food has resulted in a new fast-growing research area. Development of methods for integrated analysis of environmental and nutritional impacts is essential to facilitate policy decisions and actions for sustainable food systems. Dietary quality scores is one of the methods suggested to combine environmental and nutritional assessments of foods, meals and diets. This systematic review provides an overview of how dietary quality scores are used in environmental sustainability studies of food products and diets. The review includes 24 articles applying 20 different types of dietary quality scores. We describe current approaches used to combine environmental and nutritional assessments, discuss methodological choices of importance and their impact on results, and identify research gaps that require further efforts to push the current frontier of knowledge. Based on our analysis we identify two different categories of dietary quality scores and four approaches used to integrate environmental and nutritional assessments. There is a large number of methods available to quantify a dietary quality score: which one is chosen as well as how they are combined with environmental assessments can affect the results, and hence also the conclusions of which foods that are more sustainable to eat. This is critical to understand for the set-up of studies and for the interpretation of results and drawing conclusions. Our categorization of existing methods used, how they differ, what applications they are suited for, and which methodological challenges they involve increases the understanding of what analyzes are possible today and point out areas where methods are lacking and where more research is required. Continued efforts are needed to bring about a transition to sustainable food systems that do not exceed the planets ecological limits and promote healthy populations. This systematic review provides guidance for future use and development of methods within the field of sustainable nutrition.