A portable, low-cost, flexible, sensitive and selective paper-based sensor was proposed for nitroaromatic explosive detection in water samples. The sensor was designed to achieve pi-pi stacking formation between emaraldine base polyaniline (PANI) and pyrene (Py) molecules. This pi-pi stacking formation enables a sensitive turn-off fluorescence quenching under the principle of photo-induced electron transfer (PET) mechanism. PANI-Py absorbed paper strips were immersed into the aqueous mediums of analytes and the fluorescence quenching was observed under a simple UV lamp by naked-eye. Paper strips exhibited similar to 96% quenching efficiency and the limit of detection was calculated about 9.59 ng/ml. Self-quenching efficiency test showed that the sensor can be used for several weeks under the adequate storing conditions. In addition, experimental findings revealed that the paper-based PANI-Py strips work with high precision in real-samples such as tap water with similar to 85% quenching efficiency. Moreover the reusability investigations showed that PANI-Py paper-based sensor can be reused 5 times with 54% sensitivity.