Currently, natural bioactive ingredients and/or raw materials are of significant interest to scientists around the world. Flavonoids and other polyphenols are a major group of phytochemicals that have been researched and noted as bioactive molecules. They offer several pharmacological and medical benefits. This current review aims to (1) illustrate their benefits for human health, such as antioxidant, anti-aging, anti-cancer, anti-inflammatory, anti-microbial, cardioprotective, neuroprotective, and UV-protective effects, and also (2) to perform a quality evaluation of traditional medicines for future application. Consequently, keywords were searched on Scopus, Google Scholar, and PubMed so as to search for related publications. Then, those publications were carefully checked in order to find current and non-redundant studies that matched the objective of this review. According to this review, researchers worldwide are very interested in discovering the potential of flavonoids and other polyphenols, used in traditional medicines and taken from medicinal plants, in relation to medical and pharmaceutical applications. Many studies focus on the health benefits of flavonoids and other polyphenols have been tested using in silico, in vitro, and in vivo models. However, few studies have been carried out using clinical trials that have trustworthy subject sizes and are in accordance with clinical practice guidelines. Additionally, interesting research directions and perspectives for future studies are highlighted in this work.