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Abstract Oil‐in‐oil emulsions provide a unique platform for numerous applications not compatible with water or aqueous systems. However, the limited types and complicated synthesis process of surfactants are problematic. Here, we put forward a simple, yet powerful strategy to stabilize the oil–oil interface, then prepare oil‐in‐oil emulsions, by using the co‐assembly of polar molecular brushes and nonpolar oligomeric ligands at the DMF–octane interface. Molecular brush surfactants (MBSs) form and assemble in situ at the interface, minimizing the interfacial energy and producing a robust film. We find that the binding energy of MBS to the interface is sufficiently high, leading to the construction of structured liquids by the interfacial jamming of MBSs. Using MBSs as emulsifiers, different types of emulsions including DMF‐in‐octane, octane‐in‐DMF, and high internal phase emulsions can be easily prepared, showing promising applications in microreactor systems and advanced composite materials.