Flexible electronic devices have several advantages and multiple current or potential applications. However, the reliability and durability of their metal components (which often exist) may suffer from large and repeated strains during many applications. Carbon nanotube (CNT)-metal composite films that were laser-sintered on flexible substrates were shown to be very promising in addressing the reliability and durability issues. However, to the authors’ best knowledge, CNT–metal interfaces in a laser-sintered CNT–metal composite film on a polymer substrate and the composite–polymer interface have not been sufficiently characterized and understood. In this paper, CNT–silver composite films were produced on polyimide substrates by laser sintering, and the fabricated samples were characterized through scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Under the conditions studied, it has been found that: (1) for the CNT–silver interfaces in the composite, a significant amount of Ag–C chemical bonds is unlikely to exist, and (2) for the composite–polyimide interface, mechanical interlocking is expected to play an important role in the interfacial adhesion, while a significant diffusion of silver into the polyimide substrate is not observed. Besides, chemical reactions have likely occurred around the interface, causing the formation of Ag2O due to the reaction between silver from the composite and oxygen (in a certain form) from the polyimide substrate.