Depression is a common neuropsychiatric disorder with a multifactorial etiology and complex pathophysiology. Treatment with conventional antidepressants is often unsatisfactory and frequently associated with various adverse drug reactions. A number of plant extracts and plant-based food supplements have already demonstrated beneficial effects on the emotional and biological symptoms of depression and are widely used by patients as alternative treatments. Plant-derived biologically active substances exert anti-inflammatory and antioxidant effects and may prevent and/or reverse the neurobiochemical alterations typically associated with depression-like behavior. Animal models of depression are essential for screening the antidepressant activity of plant extracts and elucidating their underlying mechanisms of action. Among these, the chronic unpredictable mild stress model is favored by many research groups due to its reliability and reproducibility. This model successfully mimics a major etiological factor of the disorder—chronic stress—and induces core symptoms of human depression, such as anhedonia and behavioral despair. These symptoms serve as behavioral endpoints for validating the experimental model and assessing the antidepressant potential of the test compound, including the functional food of interest.