Wheat and maize are staple cereals that are each cultivated on about 200 million hectares globally. Microalgae and cyanobacteria have potential to be developed as biostimulants for wheat and maize production. This review focuses on biostimulating effects of various microalgae and cyanobacteria on seed priming, soil and foliar treatments applied in pot experiments and field trials. Two case studies on wheat and maize field trials are included. Seed priming with selected microalgal extracts is a promising method to promote plant growth but still needs validation in field trials. Soil biofertilizers based on living N2-fixing cyanobacteria (algalization) applied alone or in combination with plant growth promoting rhizobacteria modulate soil microbial composition and enhance nutrient uptake. However, this requires application of tens or hundreds kg/ha biomass to substitute for N-fertilizers so is not yet an economically viable option. The case studies indicated that a single foliar treatment of wheat at tillering and maize at the V6 growth stage with Chlorella vulgaris or Tetracystis sp. suspensions (0.1–1g DW/L applied at 400L/ha) increased grain yield, grain protein content and improve stress tolerance. These results indicated that certain microalgae could be effective biostimulants. However, producing sufficient microalgae biomass on a commercial scale is still a challenge. Monoalgal mass production in closed photobioreactors is expensive. A promising approach is the cultivation of mixed algal cultures in nutrient rich wastewater using open raceway reactors.