BackgroundContact tracing is a key control measure in the response to the COVID-19 pandemic. While quantitative research has been conducted on the psychological impact of the pandemic on other frontline healthcare workers, none has explored the impact on contact tracing staff.MethodsA longitudinal study was conducted using two repeated measures with contact tracing staff employed in Ireland during the COVID-19 pandemic using two-tailed independent samplesttests and exploratory linear mixed models.ResultsThe study sample included 137 contact tracers in March 2021 (T1) and 218 in September 2021 (T3). There was an increase from T1 to T3 in burnout related exhaustion (p < 0·001), post-traumatic stress disorder (PTSD) symptom scores (p < 0·001), mental distress (p < 0·01), perceived stress (p < 0·001) and tension and pressure (p < 0·001). In those aged 18–30, there was an increase in exhaustion related burnout (p < 0·01), PTSD symptoms (p < 0·05), and tension and pressure scores (p < 0·05). Additionally, participants with a background in healthcare showed an increase in PTSD symptom scores by T3 (p < 0·001), reaching mean scores equivalent to those of participants who did not have a background in healthcare.ConclusionsContact tracing staff working during the COVID-19 pandemic experienced an increase in adverse psychological outcomes. These findings highlight a need for further research on psychological supports required by contact tracing staff with differing demographic profiles.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12913-023-09566-6.