Understanding the allelopathic effects of invasive species on algae is essential. Therefore, this study will investigate invasive species believed to exhibit allelopathy towards algae, as listed in subsequent sections. Additionally, the ecological aspects influencing the spread of certain invasive species are highlighted. The objective of this review was to assess the allelopathic effects of alien aquatic plants found in Hungarian freshwaters. Key questions included: Which species demonstrate allelopathic effects on algae? Is allelopathy a common trait among alien aquatic plants that confers competitive advantages?