Introduction: The detection of anxiety symptoms among health workers who care for patients infected with COVID-19 is a current priority. Fast and valid instruments are required for this population group. The objective is to establish the construct validity and reliability of the Generalised Anxiety Disorder (GAD-7) scale in Colombian doctors during the COVID-19 lockdown. Methods: E-health study, in which cross-sectional data were collected online (n = 1,030) from 610 COVID doctors and 420 non-COVID doctors, during the Colombian lockdown, between 20 April and 10 August 2020. Each subject was contacted, and they confirmed their participation, identity and professional role. Results: A single factor factorial structure was found, made up of the 7 items of the instrument, which managed to explain 70% of the variance. The goodness of fit indices (RMSEA = 0.080; CFI = 0.995; SRMR = 0.053; p < 0.001) showed an “acceptable” unidimensionality and adequate factor loadings in each item of the GAD-7, >0.070. Finally, the internal consistency of the instrument was good, with a Cronbach's alpha of 0.920 (95%IC, 8.80-9.71). Conclusions: The GAD-7 is an instrument that presents adequate indicators of validity and reliability. It is an excellent tool that is reliable and easy and fast to use for the detection of generalised anxiety symptoms in medical personnel caring (or not) for patients infected with COVID-19.