“Cook and eat” meal kits from pre-packaged food delivery services provide exact portions of ingredients required for specific recipes, promoting sustainability by eliminating food waste in the cooking process. However, these services often overlook some of the current consumer behaviours associated with their use. This study aims to explore consumer behaviour regarding the use of meal kits in the Swedish context, with a particular focus on the sustainability of these behaviours. Applying activity theory as the theoretical framework, this study explores how consumers interact with meal kits during the ordering, cooking, storing and disposal and identifies potential areas for service and packaging improvement to promote sustainability. The methodology used includes a combination of qualitative survey (24 answers), in-depth interviews and observations with 4 households to gather data about consumer cooking practices and perceptions and self-reporting from 3 of the authors. Specifically, the study focuses on the operational layer of activity theory, analysing the routine actions and adjustments consumers make while interacting with meal kits, which directly and both consciously and unconsciously impact food waste and its sustainability. Considering the harmonies and tensions found between the consumer, the meal kit, including the recipe, the food, and the packaging, and the homemade meal, the findings show that while meal kits ease the cooking process and save time, they are perceived as having excessive packaging and do not completely eliminate food waste as promoted. Design suggestions include considering returnable packaging systems, offering ingredient replacement options, providing freezable and microwavable recipes, and including new cooking guidelines such as taste-testing steps. These changes can better align them with consumer needs, and potentially reduce the impact of consumer use, reducing food waste and increasing the sustainability perception of the system.