Hops (Humulus lupulus L.) are used in the pharmaceutical industry and are an essential component in the brewing industry, as they impart bitterness and aroma to beer. The increase in demand for hops due to the growth of the craft brewing industry has stimulated its expansion into new regions and countries, including Brazil. Between February and March 2023, downy mildew-like symptoms were observed in hop plants of the Cascade cultivar in an experimental area in the municipality of Guarapuava, Paraná, Brazil. During this period, 100 % of the observed plants of the Cascade cultivar showed symptoms of downy mildew and 25 % did not form cones. Hop downy mildew is an important hop disease in many growing areas around the world and is usually associated with economic losses. As there is no information or reports of downy mildew in hop in southern Brazil, this work aimed to identify the causal agent of the disease and its association with the observed symptoms. Based on morphological and molecular characterization, the pathogen associated with the symptoms was identified as Pseudoperonospora humuli (Miy. and Tak.) Wilson. This is the first report of P. humuli infecting hop plants in Brazil and its identification enables the adoption of control measures to prevent the spread of the pathogen in hop cultivation in Brazil. •Plants infected with mildew may not complete the cycle.•Hop cones infected by downy mildew are unmarketable.•The Cascade cultivar showed less tolerance to hop downy mildew.•The causal agent was identified as Pseudoperonospora humuli.•Climatic conditions in southern Brazil favor the infection of P. humuli on hops.