Behavioural economics is a discipline combining psychology and economics to understand human behaviour. This discipline found its way into several other areas to better understand this behaviour and have bigger influences on it. For marketing, this behaviour is translated to consumers that make purchase decisions. There are principles of behavioural economics such as heuristics and biases, the prospect theory or choice architecture that have impact on how consumers decide. Consumers go through a decision-making process that marketers can influence with their actions. Especially at the stage where consumers evaluate their alternatives and make the final choice, behavioural economics can have an influence. There are several attempts in marketing to integrate behavioural economics. But these are on a rather theoretical perspective. That is why this paper investigates how companies apply certain principles of behavioural economics in practice. This is done by a thematic analysis of five case studies that were provided by a German marketing consultancy and the British Institute of Practitioners in Advertising. It could be identified that the main aspect of behavioural economics that the companies focus on is that people think in comparisons and not in absolute terms. Therefore, framing seemed the most useful principle the message in a different way that makes it easier for consumers to compare it to competitors or their old behaviour. From the case studies, it could be said that the way these companies applied behavioural economics seems to be effective because all of them outperformed their set goals for the campaigns. This supports the main findings of the previous research that companies could profit from applying behavioural economics and that this enriches the existent theory in a way that could change marketing communications. The finding of a concrete model that could be applied and which principles exactly influence the consumer in which way leaves space for further research.