ObjectivesThis study aims to explore the overall and specific aspects of the functioning of medical laboratory professionals (MLPs) in Ontario, Canada during the COVID-19 pandemic.DesignA cross-sectional analysis where a questionnaire was used to assess the mental status of MLPs.SettingAn online questionnaire administered in Ontario, Canada.Participants632 MLPs (medical laboratory technologists, technicians and assistants) were included.Main outcome measuresWe employed the WHO Disability Assessment Schedule V.2.0 (WHODAS V.2.0) Questionnaire to assess functioning/disability and Copenhagen Psychosocial Questionnaire, third edition for psychosocial workplace factors. Multiple regression analysis examined the relationship between overall and specific domain functioning scores and psychosocial workplace factors.ResultsOf the total 632 participants, the majority were female gender and Caucasian. It was found that health (β=2.25, p<0.001, CI: 1.77 to 2.73), management of environmental conditions (β=0.65, p<0.001, CI: 0.33 to 0.98), fear of unemployment (β=−0.72, p<0.001, CI: −1.09 to −0.35) and frequency of stress (β=−1.86, p<0.001, CI: −2.33 to −1.40), in addition to bullying exposure (β=0.56, p<0.01, CI: 0.15 to 0.98) and threats of violence exposure (β=0.90, p<0.01, CI: 0.25 to 1.54), significantly decreased functioning overall and within the specific WHODAS V.2.0 functioning domains.ConclusionThis study provides preliminary evidence of the overall and specific aspects of functioning among the MLPs during the COVID-19 pandemic. Besides, these findings can support and guide the improvement of workplace practices and policies among MLPs in the future.