Quinoa (Chenopodium quinoa Willd.) is an emerging crop of global importance and was domesticated thousands of years ago in the Andean Region of South America. The most yield-limiting and widely reported disease of quinoa is quinoa downy mildew, caused by Peronospora variabilis. Quinoa is also affected by various fungal leaf spots and stem rots including Ascochyta leaf spot and black stem, Passalora (Cercospora) leaf spot, and Phoma stem rots. Bacterial, viral, and nematode diseases of quinoa are poorly characterized but may become more important as quinoa production spreads to new regions with different disease pressures. Management of quinoa diseases requires an integrated approach including host resistance, synthetic pesticides, biological control, cultural approaches, and seed treatments.