Algae have long been utilised as a soil amendment in agriculture due to their beneficial impact on plant health and productivity. In particular, microalgae are used as both a bio fertilizer and a bio-protectant to protect plants from phytopathogens. Algal metabolites interact with soil microbes to enhance nutrient availability by improving plant growth and development. This wide range of algae applications in agriculture opens up a lot of possibilities for screening and strain improvement programmes using better-formulated technology to understand the efficacy of marine algae. The majority of reports describe the potential of numerous algal species as bio control agents, elicitors, bio stimulants for plant growth and defence. Thus, the focus of this review will be on gaining a deeper understanding of the important applications of a broad range of marine algae in agriculture.