The COVID-19 pandemic poses a profound threat to human health across the world. A growing body of evidence suggests that dietary choice can support pandemic response efforts. This paper asks whether spirulina, a type of edible microalgae, may offer a means of reducing COVID-19 risk. This question follows from spirulina’s observed antiviral effects vis-à-vis other viral diseases. Questions about possible complementary therapies remain important due to the ongoing threat posed by COVID-19, given major gaps to vaccine rollout and the proliferation of mutant variants. The paper is based on a narrative review of the academic literature relevant to this question. The 25 papers identified were grouped and summarised, then discussed. The evidence reported suggests spirulina may have prophylactic and therapeutic efficacy against SARS-CoV-2 via several pathways, though further investigation is needed to verify the linkages identified. Incorporating spirulina into diet might thus offer a way to lower COVID-19 risk. This option may moreover be particularly helpful for at-risk populations, such as those in the Global South where many remain unvaccinated and food insecurity is widespread. This review reports findings in non-technical language and could inform actions by diverse stakeholders, including researchers, governments and households.