Molecular imprinting is a technique for preparing polymer scaffolds that function as synthetic receptors(1-3). Imprinted polymers that can selectively bind organic compounds have proven useful in sensor development(2-7). Although creating synthetic molecular-imprinting polymers that recognize proteins remains challenging(8-11), nanodevices and nanomaterials show promise in this area(12-14). Here, we show that arrays of carbon-nanotube tips with an imprinted non-conducting polymer coating can recognize proteins with subpicogram per litre sensitivity using electrochemical impedance spectroscopy. We have developed molecular-imprinting sensors specific for human ferritin and human papillomavirus derived E7 protein. The molecular-imprinting-based nanosensor can also discriminate between Ca2+-induced conformational changes in calmodulin. This ultrasensitive, label-free electrochemical detection of proteins offers an alternative to biosensors based on biomolecule recognition.