To assess transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a detention facility experiencing a coronavirus disease outbreak and evaluate testing strategies, we conducted a prospective cohort investigation in a facility in Louisiana, USA . We conducted SARS-CoV-2 testing for detained persons in 6 quarantined dormitories at various time points . Of 143 persons , 53 were positive at the initial test, and an additional 58 persons were positive at later time points (cumulative incidence 78 %). In 1 dormitory, all 45 detained persons initially were negative; 18 days later , 40 (89 %) were positive . Among persons who were SARS-CoV-2 positive , 47% (52/111) were asymptomatic at the time of specimen collection; 14 had replication-competent virus isolated . Serial SARS-CoV-2 testing might help interrupt transmission through medical isolation and quarantine . Testing in correctional and detention facilities will be most effective when initiated early in an outbreak, inclusive of all exposed persons, and paired with infection prevention and control.