In a context where macroalgae are highly valued for their versatility across multiple industries, harnessing these resources to develop sustainable products for crop protection is key. Different European crops are susceptible to bacterial and fungal pathogens that can significantly impact crop health and productivity, including mildew, powdery mildew, and botrytis, which affect a wide variety of crops due to their broad host range, adaptability, and favorable environmental conditions. This study investigates how marine macroalgae can be used as a source of active compounds such as polyphenols, polysaccharides, pigments, lectins, lipophilic compounds, alkaloids, and terpenoids against fungal and bacterial phytopathogens. Through a systematic literature review, the research assesses the infection mechanisms and susceptibility of commercial cultivars to phytopathogens and the use of macroalgae in the formulation of new sustainable bio-based pesticides. By combining a literature review with data analysis from major academic databases, this review aims to identify current knowledge gaps and suggest future research directions. The findings will highlight the potential of macroalgae as effective biopesticides with minimum impact on human and animal health and ecosystems. Moreover, it will help in the transition of agricultural practices as a solution for reducing the use and risk of chemical synthetic products for crop protection.