This review examines the impact of vesicular-arbuscular mycorrhizal (VAM) fungi on the water balance of host plants, both under ample water conditions and during drought. It summarizes published findings and suggests underlying mechanisms. Early studies suggested that VAM effects on water relations were primarily nutritional, but later research indicated that these effects can occur independently of phosphorus (P) nutrition. VAM can influence stomatal conductance, water potential, and other parameters, often leading to altered water movement into, through, and out of host plants. The review highlights that VAM can modify host water relations, even when size and P nutrition are similar between VAM and non-mycorrhizal (NM) plants. It also discusses the influence of soil drying on VAM fungi and the potential for VAM to enhance drought resistance in host plants. The review is based on over 200 peer-reviewed articles and covers a wide range of host species and VAM fungi, providing insights into the complex interactions between VAM and plant water dynamics.This review examines the impact of vesicular-arbuscular mycorrhizal (VAM) fungi on the water balance of host plants, both under ample water conditions and during drought. It summarizes published findings and suggests underlying mechanisms. Early studies suggested that VAM effects on water relations were primarily nutritional, but later research indicated that these effects can occur independently of phosphorus (P) nutrition. VAM can influence stomatal conductance, water potential, and other parameters, often leading to altered water movement into, through, and out of host plants. The review highlights that VAM can modify host water relations, even when size and P nutrition are similar between VAM and non-mycorrhizal (NM) plants. It also discusses the influence of soil drying on VAM fungi and the potential for VAM to enhance drought resistance in host plants. The review is based on over 200 peer-reviewed articles and covers a wide range of host species and VAM fungi, providing insights into the complex interactions between VAM and plant water dynamics.