Abstract: Objective To investigate the effect of heat inactivation (56 ℃ for 30 min) of SARS-CoV-2 on the results of therapeutic drug monitoring (TDM) of voriconazole by liquid chromatography tandem mass spectrometry (LC-MS/MS). Methods We collected clinical blood samples from voriconazole-treated patients in heparinized tubes and sterilized the surface of the tubes with 75% ethanol. The whole blood samples were centrifuged to separate the plasma with or without prior heat inactivation, or only the separated plasma was heat inactivated. Heat inactivation of the samples was carried out at 56 ℃ for 30 min followed by protein precipitation with acetonitrile or ethanol. The plasma standard and quality control samples were inactivated in an identical manner and tested with LC-MS/MS along with the treated samples. Results The optimized method showed a high imprecision (with mean intra- and inter-day imprecisions of 3.59% and 2.81%, respectively) and a high accuracy (mean 97.37%) for detecting voriconazole in the inactivated samples at different concentration levels. Sample preparation with acetonitrile or ethanol resulted in a high mean recovery (100.56% or 95.90% ) with minimal mean matrix effect (102.85% or 93.62% ). The measured voriconazole concentrations in inactivated whole blood, inactivated plasma and the samples without inactivation all showed good linear correlations with correlation coefficients all greater than 0.99. Conclusion Heat inactivation at 56 ℃ for 30 min combined with ethanol sample preparation only has limited effects to affect LC-MS-based voriconazole concentration measurement in whole blood samples collected in heparinized tubes, and can be used for therapeutic drug monitoring of voriconazole during the ongoing COVID-19 pandemic.