ABSTRACT In this short communication, 1-naphthaleneacetic acid (NAA), which is used as a common plant growth regulator, was tested for its effects on Drosophila, Daphnia and Saccharomyces cerevisiae. Both Drosophila and Daphnia are invertebrates, but importantly, Daphnia is aquatic. All three organisms used here are established model organisms. This plant hormone was clearly toxic for both types of invertebrate model organisms, and had growth inhibitory effect on yeast cells. In Drosophila, NAA not only caused reduction in number of larvae or pupae, but complete development was affected. Number of new Drosophila produced in next generation were very low compared to controls. Similarly, when Daphnia were cultured in presence of NAA, most of the Daphnia were dead within a week. The effects of NAA was recorded at different time points in all three organisms, and the effect was more severe at later time points, or at higher concentrations of NAA.