According to the University of California in Santa Barbara, the main difference between protista and fungi is that fungi need aerobic respiration to survive, whereas protists are able to live in an anaerobic environment without oxygen. Another difference between the two is that protists are always single-celled, but fungi can occasionally be multi-celled.
Protists and fungi are both kingdoms in the organization of all things on earth. They are similar in the way that they function and behave, but they also have their differences. They both belong to the domain of eukaryotes, which also includes plants and animals.
The protista kingdom consists of members that are autotrophic and heterotrophic. The autotrophs are able to make their own energy from sources within their body, while heterotrophs have to rely on outside sources in order to get the energy they need to survive. No other kingdom is made up of members that are both heterotrophic and autotrophic.
Fungi cannot be considered autotrophic or heterotrophic, although they more closely relate to the heterotrophs. Members of the fungi kingdom consume dead or composing material, making them saprophytes. They cannot get this material from within their own bodies like autotrophs can; rather, they get it from outside sources. Unlike heterotrophs, however, the material is not alive when they get the energy they need from it.