Interfacial tension plays an important role in the manufacture of thermoplastic matrix composites and in the development and stabilization of blend morphologies. The purpose of this work was to develop a rapid method to determine the interfacial tension. The work entailed the microscopic tracking of shape changes of polystyrene fibers imbedded in poly(methyl methacrylate). The measured interfacial tension was found to agree with a value extrapolated from literature data to ±20%. This method reduces the analysis time over traditional techniques, does not require complicated equipment, and provides reasonable precision.