Two-dimensional nanomaterials (2DNMs) have attracted increasing attentiondue to their unique properties and promising applications. Unlike 2DNMs withlamellar structures, metal ultrathin 2DNMs are difficult to synthesize andstabilize because they tend to form close-packed crystal structures. Most reportedcases consist of monometallic and heterogeneous nanostructures. The synthesisof metal alloy 2DNMs has been rarely reported. Here, we report the synthesisof PdNi alloy wavy nanosheets (WNSs) using an enhanced CO-confinementstrategy. This strategy is also suitable to the synthesis of other Pd-based alloyWNSs such as PdCu, PdFe, and even a trimetallic PdFeNi.