Genetically encoded fluorescent protein-based biosensors are widely used for pH monitoring in live cells. In this work, we have shown that fluorescent protein from Dendronephthya sp. (DendFP) has pronounced pH sensitivity. In contrast to the majority of the known genetically encoded pH-sensors, for this protein, the acidification of the environment does not lead to fluorescence quenching but just shifts it emission maximum from red to green. For this reason, it appears possible to quantitatively measure pH by the ratio of emission intensity in the red and green range, which sets DendFP apart from other pH-sensors.