The genus Perkinsus is comprised of multiple species, notably P. olseni and P. marinus that are on the list of notifiable pathogens of the World Organisation for Animal Health. These protozoans are responsible for mass mortalities in mollusc populations worldwide. Current diagnostic tests for these parasites include incubation in Ray's fluid thioglycollate medium associated with microscopy, and molecular assays such as PCR or qPCR using species-specific primers, which can be time and labour consuming. To simplify the detection of Perkinsus spp. infections, the current study developed monoclonal antibodies with strong potential for diagnostic use in immunoassays. Mice were immunised with a mix of P. olseni SA-00978-12 T isolate cell types, and multiple promising antibodies were produced through different immunoassays. The immunoglobulins developed seem to be specific to P. olseni and recognise trophozoite and hypnospore cell types. The study also highlighted the difficulty of developing antibodies against Perkinsus spp. and their different cell types and geographical isolates.