Abstract Objectives We analysed 900 samples of fresh (250) and processed (650) fish products collected in Sicily (Southern Italy) in 2020 during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic (hereafter: COVID-19). Materials and methods The samples were divided temporally based on four phases relating to the various restrictions imposed by the Italian government in this period. The validated method of ultrahigh-performance liquid chromatography combined with a diode array detector was then employed for the analysis. Results The samples collected during the Phase I lockdown period and after it had ended (Phase II) revealed significant increases in the mean histamine levels: (41.89±87.58) mg/kg and (24.91±76.76) mg/kg, respectively. The 11 (1.3% of the total) fresh fish samples that were identified as being non-compliant with Regulation (EC) No.2073/2005 were only found during these two periods. All the processed samples were always compliant. The histamine values decreased as the restrictions eased, achieving a mean value of (11.16±9.3) mg/kg (Phase III). Conclusions There was an increase in the incidence of fish samples that were non-compliant with Regulation (EC) No.2073/2005 compared to previous surveillance data. These results provide a first report on the effect of lockdown measures on food safety and the cold chain. Our findings must cause food safety operators to intensify their controls over fresh fish products in such periods to safeguard consumer health. Further studies are required to evaluate whether the same trend would be observed with other food contaminants.