A compact, reliable, and fast responsive PCF (photonic crystal fiber) based modal interferometric sensor for lead ion detection is proposed and experimentally demonstrated. The sensor has been fabricated by splicing a small section of PCF with SMF (single mode fiber) followed by collapsing the air holes of PCF at its tip. The interferometer is dip coated with chitosan-PVA (polyvinyl alcohol) and glutathione functionalized gold nanoparticles. Three probes have been fabricated, and the maximum sensitivity has been found to be 0.031 nm/ppb for lead ions whereas the detection range has been considered from 0 ppb to 50 ppb. The probe has been found to have a faster response time of ∼ 10 s. Furthermore, the sensor has been found to be less responsive towards other heavy metal ions, thereby demonstrating its selectivity towards lead ions. Besides, a section of FBG (fiber Bragg grating) has been embedded into the interferometer and the temperature response of FBG peak along with interference spectra has been investigated for better accuracy.