Heat stress is a primary abiotic stress for plant growth, particularly temperate plant species. There is increasing evidence that pre-exposing plants to mild stress (stress priming) can enhance plant tolerance to a later heat event, a phenomenon known as acquired stress tolerance. Plant tolerance to heat or thermotolerance can be improved through prior exposure to short-term, mild, or moderate levels of heat shock, drought, or cold stress. This review summarizes current literature on the effectiveness of stress priming on heat tolerance, as manifested by improved physiological health, growth and yield production in various plant species. It discusses underlying mechanisms of acquired heat tolerance through priming of plants by prior exposure to heat, drought or cold stress, focusing on molecular regulation, photosynthesis, antioxidant metabolism, hormone metabolism, and metabolic reprogramming. Additionally, this review offers future research perspectives to further understand cross-stress tolerance mechanisms and strategies for improving plant tolerance to different abiotic stress through priming.