[en] Normal-state electrical resistivity has been studied in Cu-Nb composites containing 7.5, 10.0, and 15.0 vol% niobium filaments formed by an in situ process. The resistivity of the as-drawn and annealed composite wires was measured at temperatures between 300 and 825 K and just above the superconducting transition (approx.9 K). The electron scattering from dislocations and interfaces was particularly pronounced in composites with submicron filaments and rapidly increased when the filament thickness decreased to a few hundred angstroms. The magnitude of the boundary scattering contribution in the smallest wires (25 mm in diameter) was found to be comparable to the predicted surface scattering in homogeneous copper wires of only 100 nm in diameter. In contrast to the bulk materials, dislocation scattering in highly reduced in situ composites can be the dominant scattering mechanism up to at least 300 K. These results imply a maximum dislocation density of about 10¹³ cm/cm³. The experimental findings are compared to theoretical predictions of electron scattering from one- and two-dimensional defects and correlated to the observed mechanical behavior