The excessive use of agrochemicals to ensure food security under the conditions of a growing population, global climate change, weather extremes, droughts, wasteful use of freshwater resources, and land degradation has created severe challenges for sustainable crop production. Since the frequent and abrupt environmental changes are outcompeting the existing agricultural technologies of crop production systems to meet food security, the development and use of modern technologies and nature-based solutions are urgently needed. Nanotechnology has shown potential for revolutionizing agri-production and agri-business in terms of nanofertilizers and nanoparticles for crop protection. Furthermore, in the recent past, biochar has been identified as a negative emission technology for carbon sequestration and soil fertility improvement. However, supply chain issues for biochar, due to feedstock availability, challenges its worldwide use and acceptability. Meanwhile progress in algae research has indicated that, algae can be utilized for various agro-ecosystem services. Algae are considered an efficient biological species for producing biomass and phytochemicals because of their high photosynthetic efficiency and growth rate compared to terrestrial plants. In this context, various options for using algae as a nature-based solution have been investigated in this review; for instance, the possibilities of producing bulk algal biomass and algal-based biofertilizers and their role in nutrient availability and abiotic stress resistance in plants. The potential of algae for biochar production (hereafter “phycochar” because of algal feedstock), its elemental composition, and role in bioremediation is discussed. The potential role of agal nanoparticles’ in mitigating abiotic stress in crop plants was thoroughly investigated. This review has effectively investigated the existing literature and improved our understanding that, algae-based agro-solutions have huge potential for mitigating abiotic stresses and improving overall agricultural sustainability. However, a few challenges, such as microalgae production on a large scale and the green synthesis of nanoparticle methodologies, still need further mechanistic investigation.