Piperazine designer drugs are a group of synthetic drugs of abuse that have appeared on the illicit market since the second half of the 1990s. The most common derivatives are 1‐benzylpiperazine (BZP), 1‐(4‐methoxyphenyl)piperazine (MeOPP) and 1‐(3,4‐methylenedioxybenzyl)piperazine (MDBP). They can be consumed as capsules, tablets, but also in powder or liquid forms. Generally, although less potent than amphetamines, piperazines have dopaminergic and serotonergic activities. The aim of this work was to evaluate the toxic effects of BZP, MeOPP and MDBP using Caenorhabditis elegans as in vivo model for acute toxicity, development, reproduction and behavior testing. The LC 50 for BZP, MeOPP and MDBP were 52.21, 5.72 and 1.22 mm, respectively. All concentrations induced a significant decrease in the body surface of the worms, indicating developmental alterations, and decrease in the brood size. Worms exposed to piperazine designer drugs also presented a decrease in locomotor activity and mechanical sensitivity, suggesting the possible dysfunction of the nervous system. Neuronal damage was confirmed through the decrease in fluorescence of BY200 strains, indicating loss of dopaminergic transporters. In conclusion, we suggest that piperazine designer drugs lead to neuronal damage, which might be the underlying cause of the altered behavior observed in humans.