The increasing plastic pollution and the continous dependence on fossil resources have highlighted the urgent need for the development and utilization of biodegradable plastics. Polyhydroxyalkanoates (PHAs) are promising polymers that have attracted considerable attention due to their complete biodegradability, biocompatibility, and physical properties comparable to those of conventional petrochemical based polymers such as polyethylene. These biopolymers are synthesized and accumulated as intracellular energy and carbon storage in certain groups of microorganisms and accumulate in the cytoplasm. Microalgae, which utilize sunlight as their primary energy source and require minimal nutrients for growth, have attracted attention for PHA production due to their adaptability to cultivation conditions, independence from seasonal variations, rapid growth rates. This article provides a comprehensive review of bioplastics, the conditions and metabolic pathways involved in PHA storage in microalgal cells, as well as the properties and applications of these biodegradable polymers produced by microalgae. The study also addresses commercialization, recent advancements, and associated challenges. Findings indicate that nutrient limitation significantly enhances the biopolymer accumulation in many microalgal species. Moreover, selecting appropriate microalgal strains has been shown to increase biopolymer yields as much as 70% of the dry biomass weight. The high potential of microalgae in producing biodegradable polymers could have a substantial impact on reducing environmental pollution and achieving sustainable development. Although commercial production of PHAs from microalgae still faces certain limitations, projections suggest that PHAs could account for up to 33% of the global polymer market in the future.