Dry Adhesion exists between polymer nano/microfibers. An elaborate experiment was performed to directly measure the adhesion between electrospun poly(ε-caprolactone) (PCL) microfibers using a nano force tensile tester. Electrospun nano/microfibers with radius ranging from 0.2 to 1.1 μm were investigated. It was found that the adhesion force depended on the fiber radius following a linear relationship, which complied with the classical Johnson-Kendall-Roberts (JKR) contact mechanics model. The force increased with temperature and decreased with relative humidity between two fibers positioned in orthogonal directions. Our data suggested the van der Waals’ (vdW) interactions are primarily operative between the micro-/nano-fibers.