The present study aims to investigate elementary school children’s self-control as an important aspect of their purchasing literacy in a simulated supermarket. To this end, 136 children were asked to shop on a limited budget and work through a given shopping list. We processed the data of this task in two ways: First, we combined process and product data into a common score for a differentiated assessment of task performance. Second, we derived theory-based behavioral indicators from the log data. By means of a structural equation model, we confirmed that the covariance between them could be explained by a factor of self-control. Within the structural equation model, we also investigated whether self-controlled behavior mediated the relationship between self-reported impulsivity and task performance. This could not be confirmed, even though self-controlled behavior was positively related to task performance. Self-control and impulsivity both correlated positively with a distrustful attitude toward advertising. Higher self-control was also significantly related to better monitoring one’s finances at the point of sale.