Heavy metals presence in wastewaters is a common environmental threat, since these toxic metal ions are dissolved, eventually reaching the top of the food chain and thus become a risk factor to human health and the environment. Mercury is considered a pollutant of high risk been regulated by USEPA (United States Environmental Protection Agency). The concern regarding pollution by mercury emerges of the problems to health caused for exposition to methyl mercury found in the aquatic water and foods in normal conditions. Several methods of effluent treatment like chemical precipitation, coagulation, flocculation, flotation, ion exchange, filtration are used to remove heavy metals. These methods have some drawbacks when used for treating large volumes of wastewater with low concentration of the metal. In this study we evaluated the bacterial strain Rhodococcus opacus as a potential biosorbent for mercury removal from aqueous solutions through biosorption. The pH value suitable for the biosorption of the metal was around 5. The data corresponding to the uptake capacity of Rhodococcus opacus depending on the concentration of mercury was well adjusted to the Freundlich model. The maximum uptake capacity was about: 37.9 mg.g-1 for mercury equivalent to a removal of 73.42%. The kinetics of mercury biosorption was representated by a equation of pseudo-second order. We also evaluated the surface characteristics of the microorganism before and after the interaction of metals in order to determine the possible mechanisms involved in biosorption by measurements of infrared spectroscopy. The results demonstrated that Rhodococcus opacus shows good performance as biosorbent for bioaccumulation of Hg (II).