Ultra-thin palladium nanosheets (PdNSs) with a diameter of ∼0.8 nm and characteristic (110)-oriented flat planes were synthesized by confined growth inside lamellar micelles. The rationally designed pyridinium-type surfactant with a long carbon chain (e.g., C22) is a crucial factor for the construction of PdNSs. The other synthesis parameters, including the reduction rate and concentration of reactants, should be carefully controlled. Owing to the ultra-thin feature, PdNSs performed superior electrocatalytic activity towards glycerol oxidation.