There are multiple different mold species from the Saprolegnia genus that infect fish, aquaculture and natural aquatic ecosystems. Saprolegnia parasitica is a pathogen causing infected fish to suffer from saprolegniasis, often leading to their death and thus multimillion dollar losses each year in aquaculture. In this investigation, the effect of triclosan, an antibacterial and antifungal agent, was analysed using in-solution samples of untreated and treated lab-grown S. parasitica cells with electrospray ionization-mass spectrometry. From the obtained results, a proteomic analysis was performed in order to study how triclosan affects the protein composition of the pathogen, determining if it can potentially be used to inhibit the growth of the parasite. The results from the obtained data showed a clear difference in protein composition between the triclosan treated cells and the untreated cells. Most notably, a large higher relative difference in transcription and intracellular related proteins, as well as protein types involved in proteolytic activity, were observed. In addition, a lower amount of amino acid metabolic protein types and protein types in the energy metabolic pathway were detected. However, the most unexpected result is a slight raise in relative difference in protein types associated with lipid metabolism, which is not consistent with previous findings. While the obtained results do not allow for a definitive conclusion regarding the effects of triclosan on the pathogen, they do indicate a significant impact. Further replication of the experiments is required to reach a more conclusive determination of its influence.