In this paper, a new, to the best of our knowledge, optical fluorescent sensor for the sensing of nitric oxide (NO) gas is developed. The optical NO sensor based on C s P b B r 3 perovskite quantum dots (PQDs) is coated on the surface of filter paper. The C s P b B r 3 PQD sensing material can be excited with a UV LED of a central wavelength at 380 nm, and the optical sensor has been tested in regard to monitoring different NO concentrations from 0-1000 ppm. The sensitivity of the optical NO sensor is represented in terms of the ratio I N2/I 1000p p m N O , where I N2 and I 1000p p m N O represent the detected fluorescence intensities in pure nitrogen and 1000 ppm NO environments, respectively. The experimental results show that the optical NO sensor has a sensitivity of 6. In addition, the response time was 26 s when switching from pure nitrogen to 1000 ppm NO and 117 s when switching from 1000 ppm NO to pure nitrogen. Finally, the optical sensor may open a new approach for the sensing of the NO concentration in the harsh reacting environmental applications.