Sustainable and healthy food-related behavior is high on the public policy and research agenda due to its potential to cope with negative environmental and health outcomes. There are several measures related to sustainability in food choices but there have not been many attempts to integrate sustainable and healthy eating (SHE) behaviors into one measurement instrument so far. Therefore, the main aim of this study was to identify how young adults interpret the SHE concept and to develop an instrument that measures a self-reported consumer’s SHE behavior. The process of scale development involved an exploratory qualitative study and two quantitative studies. As a result of 20 individual in depth interviews with Polish young adults, 50 items were generated reflecting their perspective on principles of SHE (Study 1). Two samples were used in the scale validation process: n = 217 (Study 2) and n = 220 (Study 3). Via principal component analysis, reliability analysis, and confirmatory factor analysis, the final form of the scale was derived. The proposed 34-item scale offers insights into the most relevant aspects of SHE behaviors, grouped in eight factors: “healthy and balanced diet”, “certification and quality labels”, “meat reduction”, “selection of local food”, “choice of low fat food products”, “avoidance of food waste” and purchase and consumption of food products that are respecting “animal welfare” and finally choice of “seasonal food”. Although the developed scale can benefit from further refinement and validity testing in different cultural and social background, it is clear that the scale, as developed, can be a useful tool for researchers who are interested in the study of SHE behaviors.