The αvβ3 and α5β1 integrins are widely expressed in different cancer types and recognize the tripeptide Arg-Gly-Asp (RGD) motif present in several extracellular matrix proteins. We report here the design, synthesis and biological activity of some new β-lactam derivatives specifically designed to target integrins. The new molecules contain the azetidinone as the only cyclic framework armed with carboxylic acid and amine terminals spaced from 9 to 14 atoms to switch on recognition by integrins. All tested molecules showed a concentration-dependent enhancement in fibronectin-mediated adhesion of K562 and SK-MEL-24 cells; in particular 1, expressed a higher affinity towards α5β1 integrin (EC50 of 12 nM) and 2 was more selective for integrin αvβ3 (EC50 of 11 nM).