Contemporary society is plagued with uncertainties and vulnerabilities, demanding from regulatory systems the surveillance of unregistered and/or falsified medicines sold online. This study investigates the work of federal health surveillance professionals in the inspection of medicines sold online and the elements that guide their technical decision. A qualitative, single case study based on the ergological approach was conducted between December 2020 and September 2021, with data collected by interviews and participant observation. Ergodialogical maps, developed using Atlas.ti, underlined the analysis of discursive practices classified according to the tri-polar knowledge-action-value schema, resulting in three categories. Professionals are always called upon to decide on and manage unpredictable situations, questioning the institutional capacity to understand and act on the problem. The work thus takes on the sense of “rolling a stone uphill” due to the volume of demands and the limited effects of surveillance on the e-commerce of medicines. Norms, technical knowledge, experience, and social responsibility, among other elements, inform the decision-making process of professionals, who are aware that, by acting, they protect public health. Different forms of knowledge, scientific or experiential, can better qualify decision-making in surveillance, making it more effective, assertive, and transparent.