BACKGROUND: As population and fuel demand increase, many events of oil spills in the environment have been recorded. In order to restore these environments, several techniques have been proposed in the literature, especially in the field of bioremediation, with their main advantage being a low impact on the environment. In this work, poly(butylene succinate) microspheres containing urea were produced, representing a source of controlled release of nitrogen to the environment, promoting the biostimulation of the native microbiota of contaminated sites. Experiments were conducted based on the biostimulation of Pseudomonas aeruginosa and assessed the growth of the culture, the controlled release of urea, the substrate consumption and the toxicity of the microspheres using Artemia salina. RESULTS:The results showed that the double-emulsion methodology for urea encapsulation was efficient, with controlled release occurring up to 72 h. The urea-containing microspheres promoted microbial growth with higher protein synthesis (198.66 ∼g mL −1 ) in 72 h, from the consumption of glucose and urea, within the release limitations. The ecotoxicity of the urea-containing microspheres was tested with A. salina and the results showed a CL50 of 0.027 mg (10 mL) −1 , not recommending its use in the aquatic environment for this organism. CONCLUSIONS:The assays revealed that poly(butylene succinate) microspheres, both with urea and without this active ingredient, may not present toxicity to microorganisms such as P. aeruginosa and be toxic to more complex organisms such as A. salina.