Studies were carried out to develop all solid contact cesium ion selective electrode with 25,27-bis(1- octyloxy)calix[4]arene-crown-6 as an ionophore. Polyaniline (PANI), deposited on Pt electrode by electrochemical method, was used as a transducer. Three different types of electrodes were made with variation in thickness of PANI film and gold nanoparticles doped PANI as transducers. The best response was observed with ISE having Au nanoparticles doped PANI as a transducer. The optimised ISE gave Nernstian response in the range 10^-7 to 10^-2 M with the slope of 55.0 ± 0.6 mV/decade of Cs⁺. The response of ISE for Cs⁺ is fairly constant above the pH 4. The developed ISE was successfully employed to determine Cs? in simulated high level nuclear waste solutions and CsCl spiked tap water samples.