This article tries to solve two of the problems that are noticed in the interpretation of the administrative contract, given the normative dispersion and the lack of contentious-administrative courts that allow condensing this matter. A first problem is the indeterminacy of the legal regime applicable to administrative contracts in the execution phase, for which, based on the previous contributions of the doctrine, I am going to start by proposing criteria that allow to differentiate between the administrative contract in the strict sense and the private contract of the Administration. A second problem is the preeminent use of civil rules that, together with the alleged general supplementary nature of the Civil Code, raise the need to review the supplementary legal status of administrative contracts in silence of express rule, for which I am going to base the interpretation based on the rules and principles of contracting in public law and the supplementary application of civil rules in the absence of the foregoing.