An effective control of the COVID-19 pandemic requires a thorough epidemiological interview of reported cases. The interviewer's skills and preparation directly affect the outcome of the investigation. This study applied a self-assessment survey of the COVID-19 patient interviewing skills on a local public health department workforce. The findings may be used to improve the quality of the interview process and the overall response to the pandemic at a community level. A 50-item questionnaire using a four-point Likert scale was adapted from the COVID-19 Patient Interview Skills Assessment Form created by the Centers for Disease Control and Prevention (CDC) and applied to 50 healthcare workers involved in epidemiological investigation of COVID-19 cases in Almada and Seixal, two municipalities of the Lisbon Metropolitan Area, from January to April of 2021. The most frequently executed steps concern checking patient data in advance (92%), questioning symptoms (97.2%), contact tracing (100%) and determining isolation periods for high risk contacts (100%). Least performed tasks include confirming the testing technique used (50%), asking about hospitalization (44.4%), assessing conditions for home isolation (44%), explaining how to self-monitor symptoms (61%) and checking if the patient understood the instructions (47%). In addition, 8% admitted to not always keeping patient information confidential. While caution is necessary as the data was limited to a single public health local department, our findings show that a majority of healthcare workers fulfill the essential steps of an epidemiological investigation. Areas in need of improvement include inquiring about infection severity, assessing social conditions for quarantine and confirming instructions for self-monitoring and follow-up. In line with CDC recommendations, we believe regular evaluation and feedback of case investigators' skills are crucial to quality assurance of a public health department.Key messages A detailed interview provides critical data for monitoring infected individuals and quickly trace, test and isolate those who might have been exposed, thus breaking chains of transmission.The results of this assessment can be used to introduce training measures such as shadowing and role-playing to ensure continued improvement in epidemiological investigations.