Seaweed-based biostimulant production is a growing industry in the last decade due to the advantages of biostimulant application on crops. Here we summarise the current findings of using these seaweed extracts (SE) and highlight current knowledge gaps. SE can boost seed germination, promote reproductive development (budding and flowering), facilitate vegetative growth, modify shoot and root system architecture, improve protein content, and enhance fruit taste and quality. Certain SE also contribute to a healthy soil by facilitating water retention, soil aeration and nutrient availability, thereby promoting plant growth. Although seaweeds have been proposed as alternative protein food sources, the use of seaweed extracts to instead boost yield and protein production in crops may be a more efficient way to meet growing food demand. We are highlighting the potential of SE for increased productivity, especially in crops exposed to abiotic stress.