In this study, we propose that a molecular junction with a sharp Negative Differential Resistance (NDR) current peak could improve the selectivity, thereby functioning as a potential molecular sensor for molecule recognition. Using DFT–NEGF simulations, we investigate the connection between molecule–molecule coupling, molecule–electrode coupling and the corresponding NDR peak shape. Based on this analysis we propose three design rules to control the sensitivity of a sensor and determine that one mechanism for NDR is for a localised molecular orbital involved in resonant tunneling to enter and leave the bias window. Our findings provide useful insight into the development of single molecule sensors for molecule recognition.