Prototheca are ubiquitous algae and occasional pathogens of humans and animals. While rare, the infection is often fatal and treatment options are limited to antifungals with low efficiency. Here, using growth curve assays, we demonstrate that five pathogenic species of Prototheca (P. blaschkeae, P. wickerhamii, P. cutis, P. ciferrii, P. bovis) were fully inhibited by 50–100 μg/mL of herbicide glyphosate, suggesting novel pathways that can be considered for anti-algal drug development.