Hydroxychloroquine (HCQ) has shown efficacy against coronavirus disease 2019 (COVID-19) in some but not all studies. We hypothesized that a systematic review would show HCQ to be effective against COVID-19, more effective when provided earlier, not associated with worsening disease and safe. We searched PubMed, Cochrane, Embase, Google Scholar and Google for all reports on HCQ as a treatment for COVID-19 patients. This included preprints and preliminary reports on larger COVID-19 studies. We examined the studies for efficacy, time of administration and safety. HCQ was found to be consistently effective against COVID-19 when provided early in the outpatient setting. It was also found to be overall effective in inpatient studies. No unbiased study found worse outcomes with HCQ use. No mortality or serious safety adverse events were found. HCQ is consistently effective against COVID-19 when provided early in the outpatient setting, it is overall effective against COVID-19, it has not produced worsening of disease and it is safe.