Marine environments are rich in microbial diversity and present an untapped reservoir of bioactive compounds and metabolic pathways. This chapter explores the bioprospects of marine microbes and presents a promising frontier for enhancing plant growth and controlling diseases. Marine bacteria, fungi, and actinomycetes promote plant growth, including phosphate solubilization, nitrogen fixation, the synthesis of antimicrobial chemicals, and siderophore production. Plant diseases can be significantly controlled by various plant mechanisms, such as biofertilizers, plant growth-promoting rhizobacteria (PGPR), antagonism, induced systemic resistance (ISR), biocontrol products, biological soil amendments, biological seed treatments, synthesis of lytic enzymes, and integrated pest management (IPM). This chapter also explores the applications of marine microbes in agriculture as biofertilizers, biostimulants, biocontrol agents, bioremediation agents, and climate change adaptation agents. Additionally, it addresses future challenges and available prospects. This chapter highlights the untapped potential of marine bioprospects in the development of eco-friendly agricultural practices and the role of marine microbes in enhancing plant growth and providing sustainable disease management solutions, offering a viable alternative to chemical fertilizers and pesticides.