Control of the location and spatial organization of nanoparticles (NPs) inside polymers is essential to generate highly ordered NP-based functional devices including plasmonic waveguides, photonic crystals, optical lenses, memory storage devices, nanoelectronic circuits, photovoltaics, and batteries. Due to the unique combination of amphiphilicity and the particle character, Janus nanoparticles (JNPs) show high interfacial activity at fluid–fluid interfaces and in the bulk (for example, polymer blends and block copolymers (BCPs)). Interfacial incorporation of Janus NPs inside a polymeric matrix can endow polymeric materials with improved mechanical and additional properties from ordinary NPs. Here, different from other reports providing general overviews on the synthesis and applications of JNPs, this review specifically highlights recent advances and success in interfacial behavior of Janus NPs at polymer interfaces. We hope that these accomplishments will motivate additional efforts in large-scale synthesis and interfacial behavior studies of Janus NPs in polymer matrices allowing the design of functional hybrid nanostructures and devices with engineered, desired and tailored properties for real-life applications.