This systematic review critically examines existing literature on the effects of spontaneous fermentation on the nutritional and antinutritional properties of the aforementioned food staples, focusing on the changes in nutrients, digestibility, and antinutrients. The literature search flow was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRiSMA-2020) approach. Only peer-reviewed journal articles published in English between 2002 and 2024 were sourced from Scopus, Web of Science, and PubMed. A total of 67 articles were considered eligible after the title, abstract, full text, and quality assessment. It was evident from the various studies consulted in this review that traditional fermentation, though being an ancient food processing practice, remains an important approach for increasing the level of nutrients, reducing antinutritional factors, and enhancing the nutrient digestibility of cereals, legumes, roots, tuber, and plantain. This has made fermented foods an important part of diet and nutrition in many cultures around the world, especially in the global south, with limited access to sophisticated food processing techniques and infrastructure. Overall, the findings suggest that incorporating spontaneous fermentation into the preparation of cereals, legumes, roots, and tuber crops can be a valuable strategy for enhancing the nutritional value and health-promoting properties of these dietary staples.