This cross-sectional study aimed to (1) describe the unclassified contents of telephone consultation services provided by a public health center during the first wave of COVID-19 in Japan and (2) examine whether the contents required assistance from public health nurses (PHNs). We analyzed a total of 207 calls in which the purpose of the call was unclassified into pre-set categories. PHNs transcribed the exact text of the consultation conversations recorded from 25 March to 20 April 2020 in City A. Approximately half of the calls were from residents. Seven categories were extracted through a qualitative content analysis. The most common topic was infection control measures, where the presence of COVID-19 infection was assumed (n = 62); the second most common was extreme anxiety and fear of infection (n = 50). Questions about the COVID-19 response system (n = 30), discrimination and misunderstandings about COVID-19 (n = 24), and response measures for COVID-19 outbreaks within organizations (n = 18) were also included. The unclassified consultations included various topics, several of which required the expertise of a PHN. Each local government should consider sharing and task-shifting telephone consultation services among PHNs and other staff to reduce their burden and allow them to concentrate on conducting infection control more effectively.