We report the sensitivity of Iron CALorimeter (ICAL) detector to the detection of TeV gamma rays from various astrophysical sources at India-based Neutrino Observatory (INO). The ICAL detector is proposed to be of 51 kton with an average magnetic field of ~ 1.3T. The electromagnetic showers generated by high-energy gamma rays at the atmosphere will produce down-going muons through either muon pair production or pion decay. The gamma rays can be traced by detecting these muons using ICAL. Most of the space- and underground-based experiments have detected them directly and indirectly, but the advantage of using ICAL for their detection is to measure the µ+ to µ- ratio, which is 1in case of pair production, at very high energy (≥ 50 GeV). Here, we have shown its detection ability for the appropriate astrophysical 2FHL sources listed in “The Second Catalog of Hard Fermi-LAT Sources,” where the signal-to-noise ratio is suppressed by factor of 5σ for ICAL running period of five years for spectral index of ≥ 0.45. © Springer Nature Singapore Pte Ltd 2018.