The undiscriminating exploitation of different chemical fertilizers/pesticides for boosting agricultural productivity has given rise to severe issues such as accumulation of poisonous pollutants. Such issues cause ecological imbalance among soil, plant, as well as microbiota, thereby affecting the fertility and health of the soil. However, sustainable agriculture is straightforwardly dependent on soil health. The soil health involves the capability of the soil in establishing ecological quality, sustaining bio-productivity, as well as maintaining health of all living things. Soil health is closely linked to sustainable agriculture as soil microbe variety and activity have been the key constituents of soil health. In this context, the algae (microalgae and cyanobacteria) of soil perform a key functions toward maintaining the nutrient balance (in case of nitrogen, phosphorus, potassium, and carbon) as well as soil health. These maintain the fertility and health of soil in both living and dead conditions. This chapter is an attempt to highlight the major role of soil algae toward the sustenance/maintenance of soil health, fertility, and agricultural productivity.