Natural fibers from plants are ideal choice for producing polymer composites. Bark fibers of Prosopis juliflora (PJ), an evergreen plant have not been utilized for making polymer composites yet. Hence, a study was undertaken to evaluate their suitability as a novel reinforcement for composite structures. PJ fiber (PJF) was analyzed extensively to understand its chemical and physical properties. The PJF belonged to gelatinous or mucilaginous type. Its lignin content (17.11%) and density (580 kg/m(3)) were relatively higher and lower, respectively in comparison to bark fibers of other plants. The free chemical groups on it were studied by FTIR and XRD. It had a tensile strength of 558 +/- 13.4 MPa with an average strain rate of 1.77 +/- 0.04% and microfibril angle of 10.64 degrees +/- 0.45 degrees. Thermal analyses (TG and DTG) showed that it started degrading at a temperature of 217 degrees C with kinetic activation energy of 76.72 kJ/mol. (C) 2012 Elsevier Ltd. All rights reserved.