Pumpkins, as well as all other squashes are considered fruits. Fruits are defined as "the fleshy or dry ripened ovary of a plant, enclosing the seed or seeds," by the Encyclopedia Britannica. As a rule, fruits have visible seeds which means beans, tomatoes, cucumbers, peppers, olives, avocados, and pumpkins are all fruits. Another fun fact: big pumpkin, mini pumpkins, acorn squash, spaghetti squash, zucchini, and ornamental gourds are all different cultivars of the same species: Curcurbita pepo, which originated in Mexico more than 10,000 years ago.
(Yahoo)