The COVID-19 global pandemic is now a public health emergency in Morocco. Reports on factors associated with prolonged viral shedding are not consistent. In this retrospective laboratory based study, time to RNA negative conversion is reported in a series of 129 patients monitored in a single laboratory in Casablanca. Risk factors associated with delayed negative conversion have been evaluated, by chi-squared test. Median delay of negative conversion was 22.5 days (IQR 17.75-29.0) from illness onset. Neither gender nor age were particularly associated with delayed viral clearance. Delayed time to hospital admission and disease severity were associated with prolonged viral shedding in this series. We recommend early diagnosis and treatment onset to reduce time to viral clearance and transmissibility of SARS-CoV-2 virus.