The health emergency linked to Covid-19 brought to the fore the problem of the usefulness and correct application of the precautionary principle. In the paper proposed for the call, the topic will be analyzed starting from the foundations of the precautionary principle, to see consequently how it must be ‘handled’ in practice when the Administration (in the Italian fight against the pandemic, the Government, but also the Regions) is called to decide in contexts of health crisis. Particular attention will be paid, just from the beginning, to the relationship between science and Public Administration, in order to demonstrate how the precautionary approach represents a ‘rule of action’ for the public decision-maker when there is no full scientific certainty. In this perspective, the analysis will be developed starting from the definition of a general context: that one represented by the so-called ‘irreducible uncertainty.’ This premise will be the starting point to define a law of uncertain science,’ which ‘follows’ the facts and is characterized for its flexibility. The problem will then be reported to the administrative decisions, called in emergency times to be ‘adaptive’ and reviewable. The reflection on precaution ‘in action’ will have the Italian case as an observation ‘laboratory.’ In this perspective, the investigation will be conducted by looking at the ‘answer’ of the Italian legal system to the emergency related to Covid-19. This will lead to see if the precautionary approach has been taken seriously by the Italian Administration and, subsequently, what characters have taken the measures to fight against the spread of the Coronavirus outbreak. In conclusion, it will be necessary to understand whether the ‘postulates’ of precaution ‘in the books’ have been translated into an adequate precaution ‘in action.’ In other terms, the attention will be focused on two different aspects: the first related to the ‘time’ of the action; the second to the content of the measures taken to fight against the spread of the virus. This will allow us to understand if the Italian Government acted promptly (in compliance with the precautionary approach) and what was the decision-making process that brought to these measures.