Microencapsulation of carbon nanofibers (CNFs) suspended in an organic phase with a polymer shell of poly(urea-formaldehyde) by in situ polymerization has been carried out. The encapsulation efficiency of CNFs and ethyl phenylacetate (EPA), the morphology and the particle size distribution of the obtained microcapsules were determined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), optical microscopy (OM), environmental scanning microscopy (ESEM), laser diffraction and mercury porosimeter. TGA and DSC data were in agreement with the OM and ESEM analysis demonstrating that the synthesized microcapsules consisted of poly(urea formaldehyde) (shell material), EPA and small amount of CNFs (core materials). Furthermore, the presence of nanopores in the shells of obtained microcapsules provides a versatile platform for the further development of numerous promising applications. The influence of the CNFs weight fraction in the core material on the encapsulation efficiency, the morphology and the particle size distribution were also studied. The amount of CNFs does not have a significant effect on the encapsulation of EPA. Microcapsules containing CNFs and EPA as core material had a particle size bigger than microcapsules only containing EPA. These microcapsules containing CNFs could be considered to have potential as structural materials, electrochemical sensors, field emission displays and nanometer sized semiconductor devices. (C) 2011 Elsevier B.V. All rights reserved.