Agaricus bisporus is the most economically significant edible mushroom produced globally. Button mushroom is a basidiomycete mushroom native to grasslands in Eurasia and North America. While it is cultivated in over 70 countries, its production is frequently threatened by Pseudomonas tolaasii, a bacterium endemic to the compost beds. Under some environmental conditions still not well-determined, but influenced by temperature and relative humidity, the bacterium can become pathogenic and provoke the brown blotch disease. This review describes the interaction between P. tolaasii and A. bisporus that results in the appearance of brown spots on the mushroom caps, typical symptoms of the disease. This study examines P. tolaasii, detailing shifts in pathogenicity and categorizing the specific compounds responsible for tissue damage, alongside various experimental diagnostic methods. Subsequently, it addresses the mechanisms behind the browning of A. bisporus caps during infection.