Professional helpers, including treatment (“correctional”) staff employed in the penal system, are obliged to provide help and assistance in facilitating the problems with which the users of their services are faced. However, in the process they themselves are without doubt exposed to major workplace stress, which as a consequence can lead to burnout syndrome. Characteristic of the professional burnout syndrome is its presence among various helping professions, among which numerous studies have been conducted. The main purpose of this paper is to contribute in a better understanding of the professional burnout of the penal staff in general, as well as of the treatment staff of the penal system in Croatia in particular. The project “Support of prison and probation officers through supervision” has included the convenience sample of N = 78 prison and probation officers in Croatia. Within the project and for the purposes of assessing the professional burnout, Maslach Burnout Inventory (MBI-HSS, Maslach and Jackson, 1981) was used. The assessment was conducted before and after the implementation of the project activities and hence the results are obtained before and during the COVID-19 pandemic in 2020. Prison and probation officers mostly are reporting about low personal accomplishment which on average occurs several times a month to each week. This indicates about significant incidence of professional burnout symptoms. With the outbreak of the pandemic, the incidence of low personal accomplishment has increased, while there were no statistically significant changes on the other two dimensions - emotional exhaustion and depersonalization.