Water-soaked brown flesh disorder of peach (Prunus persica (L.) Batsch) fruit, which occurs in unpicked fruit near harvest time, has been a problem in Japan since the 1990s. The affected fruit share the characteristics of more mature fruit in that the fruit are large, sweet, and soft. It has also transpired that high-quality; high-value fruit are more sensitive to the disorder, which exacerbates economic losses. The most susceptible regions of the fruit are those with high sugar content, although the symptoms are not clearly linked to specific cultivars. Investigations into the cause(s) of water-soaked brown flesh disorder of peach fruit have just started, and reports are limited to Japan. In this review, published information about the disorder is reviewed, and a hypothesis for the occurrence of water-soaked brown flesh disorder in peaches is presented.