The proposed 50 kTon magnetised Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) aims to detect atmospheric neutrinos and study the effect of Earth matter on their propagation and determine neutrino mass hierarchy. In addition to performing standard oscillation studies, ICAL can probe exotic phenomena like neutrino decay. A study of the sensitivity of the 50 kTon to the invisible decay
of the mass eigenstate ν3 is studied. A full three-generation analysis including earth matter
effects is performed in a framework with both invisible decay and oscillations. The wide energy range and baselines offered by atmospheric neutrinos are shown to be excellent for constraining the ν3 lifetime. It is found that with an exposure of 500 kton-yr, ICAL will be able to constrain the ν3 lifetime to τ3/m3>1.51x1010 s/eV at the 90\% C.L by analysing charged current νμ + anti-νμ events. This is two orders of magnitude tighter than the bound from MINOS. The effect of invisible decay on the precision measurement of θ23 and Δm32 is also studied.