Spiny lobster, Panulirus homarus is an economically important fishery product which indicated by huge demand of this species at both local and International markets. However, high mortalities were recorded during grow-out period due to infection of diseases. This study was conducted to investigate disease occurrences in grow-out of P. homarus cultured in floating net cages. The study was done throughout collection of samples, observation of parasites, isolation of fungi and bacteria, and detection of Milky Hemolymph Disease of Spiny Lobster (MHD-SL) by PCR. The samples were obtained from Lombok, Pangandaran, and Pegametan (Bali), five lobsters each. Results showed that three lobsters from Pangandaran were infected with ectoparasite Octolasmis sp. that infect mostly in the gill lamellae. One sample from Lombok was found to be infected with Fusarium sp., the causative agent of black gill disease which indicated by black coloration of the gill. Detection of milky disease showed that one lobster from Pegametan and two lobsters from Lombok were infected with the disease. Milky disease is the most devastating disease which causing in high mortalities within 5 days of the onset of symptoms of milky disease infection. Considering that MHD-SL can be transmitted rapidly, it is suggested to perform biosecurity and quarantine procedures immediately to prevent disease translocation.