(1) Background: The emergency linked to the spread of COVID-19 in Italy has led to inevitable consequences on the penitentiary system. The risks of this emergency in prisons is mainly related to the problem of persistent overcrowding that makes social distancing difficult and the isolation of any contagion hard to arrange. The Department of Protection for Adults and Minors of the ASL Salerno Criminal Area has taken steps in order to perform screening operations and minimize the risks for prisoners and operators. (2) Methods: We conducted a two-phase observational study. In the first phase, we offered and then executed serum COVID-19 screening to all the convicted inmates. For those who had a doubtful or positive result, a swab was executed in the shortest time possible. In the second phase, a pharyngeal swab was offered and executed to all the police officers, the penitentiary administrative staff and the medical personnel working in the prison. (3) Results: In the first phase, we executed 485 COVID-19 blood tests on prisoners, 3 (0.61%) of which were positive. The three positive inmates underwent nasopharyngeal swabbing, which ultimately were negative. After that, we executed 276 nasopharyngeal swabs on the prison personnel, penitentiary administrative staff and medical personnel—all were negative. (4) Conclusion: All tests (blood tests and swabs) that were carried out on the prisoners and on the staff were negative for COVID-19. We believe that all prisons in Italy and in the world should take action to ensure preventive and control measures in order to safeguard the health of the prison population and of all the people who work there.