The molecular square [Re(CO)3Cl(L)]4 (1) containing the dipyridyl-amide ligand, N,N′-4-dipyridyloxalamide (L), was constructed from Re(CO)5Cl and L for the purpose of anion-recognition studies. Upon addition of fluoride anions to a THF solution of 1, a remarkable spectral change is observed, and indeed a new absorption band grows at ca. 348 nm. We reasoned that upon addition of fluoride, the hydrogen bonds between F− and –NH groups of L would first form and increase the electron densities of nitrogen atoms. This in turn increases the conjugation throughout the L ligand, which is responsible for the new growing absorption band. Finally, a proton-transfer process occurs upon addition of excess F− anions, corroborated by the 1H NMR titration experiment due to the occurrence of HF2−. The binding constants based on a 1 ∶ 1 complex (1–X−, X− = anions) follow the order: F− > CN− > OAc− > Cl− > Br−, PF6−, BF4−, ClO4−, NO3− and HSO4−. The most electronegative F− anion shows the largest binding constant, followed by CN−, OAc− and Cl− anions. The less electronegative Br− anion and bigger PF6−, BF4−, ClO4−, NO3− and HSO4− anions do not show any binding affinity with 1. The control titrations carried out using L and the same series of anions showed that the basicity of anions also possibly lends some contribution to the sensing events. However, the binding affinity of 1 toward various anions can be mostly correlated with the electronegativity as well as cavity size of the molecular square, and hence 1 can be expected to be a sensor for F−.