This report describes the investigation of presymptomatic transmission of SARS-CoV-2 in Singapore from January 23 to March 16, 2020. The first case was detected on January 23, and by March 16, 243 cases were confirmed, including 157 locally acquired. Clinical and epidemiologic data were reviewed to determine if presymptomatic transmission occurred. Seven clusters were identified where presymptomatic transmission likely occurred, accounting for 6.4% of the 157 locally acquired cases. In four clusters, presymptomatic transmission occurred 1–3 days before symptom onset in the source patient. These findings suggest that presymptomatic transmission is a significant factor in the spread of SARS-CoV-2, highlighting the importance of social distancing and avoiding congregate settings. Public health officials should consider including a period before symptom onset in contact tracing protocols to account for this possibility. The study also notes that presymptomatic transmission may occur through respiratory droplets or indirect transmission. The findings support the likelihood that viral shedding can occur before symptom onset, emphasizing the need for comprehensive containment measures. The study has limitations, including the possibility of unknown sources and recall bias in symptom onset dates. Overall, the evidence of presymptomatic transmission underscores the importance of public health measures to control the spread of SARS-CoV-2.This report describes the investigation of presymptomatic transmission of SARS-CoV-2 in Singapore from January 23 to March 16, 2020. The first case was detected on January 23, and by March 16, 243 cases were confirmed, including 157 locally acquired. Clinical and epidemiologic data were reviewed to determine if presymptomatic transmission occurred. Seven clusters were identified where presymptomatic transmission likely occurred, accounting for 6.4% of the 157 locally acquired cases. In four clusters, presymptomatic transmission occurred 1–3 days before symptom onset in the source patient. These findings suggest that presymptomatic transmission is a significant factor in the spread of SARS-CoV-2, highlighting the importance of social distancing and avoiding congregate settings. Public health officials should consider including a period before symptom onset in contact tracing protocols to account for this possibility. The study also notes that presymptomatic transmission may occur through respiratory droplets or indirect transmission. The findings support the likelihood that viral shedding can occur before symptom onset, emphasizing the need for comprehensive containment measures. The study has limitations, including the possibility of unknown sources and recall bias in symptom onset dates. Overall, the evidence of presymptomatic transmission underscores the importance of public health measures to control the spread of SARS-CoV-2.