Macrobrachium rosenbergii is the species most favoured for freshwater shrimp farming purposes and remains by far the major subject of cultivation for commercial farming. Despite their innate defences and natural immunity, shrimp farms have been experiencing decreased production brought about by viral and bacterial disease outbreaks. One of its bacterial pathogens, Vibrio alginolyticus, is responsible for vibriosis, a disease causing high mortality in cultured shrimps worldwide. Here, we report for the first time the efficiency of hot-water extracts from Gracilaria edulis, a red algae species abundantly distributed all over the country, as an immunostimulant for the shrimp M. rosenbergii. Immune parameters, including total hemocyte count (THC) and phenoloxidase (PO) activity were examined, as well as resistance to V. alginolyticus infection. An increase in THC and greater PO activity compared to the control group was observed upon immersion in tanks with G. edulis hot-water extracts. Shrimps immersed in 0.1g/L dosage significantly increased percentage survival at the end of the challenge test, highlighting its capability in inducing bacterial resistance particularly against V. alginolyticus. Overall, the results demonstrated that exploring the Philippine Gracilaria species and their application as immunostimulant might pave the way for the development of local feeds for the country’s aquaculture industry.