A mixotroph is an organism that uses a mix of different sources of energy and carbon, instead of having a single trophic mode. Mixotrophs are situated somewhere on the continuum from complete autotrophy to complete heterotrophy. It is estimated that mixotrophs comprise more than half of all microscopic plankton. There are two types of eukaryotic mixotrophs. There are those with their own chloroplasts – including those with endosymbionts providing the chloroplasts. And there are those that acquire them through kleptoplasty, or through symbiotic associations with prey, or through 'enslavement' of the prey's organelles.

Possible combinations include photo- and chemotrophy, besides litho- and organotrophy, the latter including osmotrophy, phagotrophy and myzocytosis. Mixotrophs can be either eukaryotic or prokaryotic. Mixotrophs can take advantage of different environmental conditions.

A given trophic mode of a mixotroph organism is called obligate when it is indispensable for its growth and maintenance; a trophic mode is facultative when used as a supplemental source. Some organisms have incomplete Calvin cycles, so that they are incapable of fixing carbon dioxide and must use organic carbon sources.

Organisms may employ mixotrophy obligately or facultatively.

Amongst plants, mixotrophy classically applies to carnivorous, hemi-parasitic and myco-heterotrophic species. However, this characterisation as mixotrophic could be extended to a higher number of clades as research demonstrates that organic forms of nitrogen and phosphorus—such as DNA, proteins, amino-acids or carbohydrates—are also part of the nutrient supplies of a number of plant species.

Mycoheterotrophic plants form symbiotic relationships with mycorrhizal fungi, which provide them with organic carbon and nutrients from nearby photosynthetic plants or soil. They often lack chlorophyll or have reduced photosynthetic capacity. An example is Indian pipe, a white, non-photosynthetic plant that relies heavily on fungal networks for nutrients. Pinesap also taps into fungal networks for sustenance, similar to Indian pipe. Certain orchids, such as Corallorhiza, depend on fungi for carbon and nutrients while developing photosynthetic capabilities (especially in their early stages).

Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods, and occasionally small mammals and birds. They have adapted to grow in waterlogged sunny places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic bogs.

Hemiparasitic plants are partially parasitic, attaching to the roots or stems of host plants to extract water, nutrients, or organic compounds while still performing photosynthesis. Examples are mistletoe (absorbs water and nutrients from host trees but also photosynthesizes), Indian paintbrush (connects to the roots of other plants for nutrients while maintaining photosynthetic leaves), and Yellow rattle (a root parasite that supplements its nutrition by tapping into host plants).