Studies on the Mn-substitution induced modification in the structural, thermal, magnetic and magnetocaloric properties of TbCrO3 orthochromite are presented. The phase formation and purity of the samples were examined by analyzing X-ray diffraction (XRD) patterns. Magnetization measurements as a function of temperature reveal the antiferromagnetic ordering of Cr3+ spins (TN1) at ∼ 157 K and Tb3+ spins (TN2) ∼ 5 K for TbCrO3 sample. The substitution of Mn-atoms at Cr-site results in a decrease in TN1 whereas an increase in TN2. The isothermal magnetization measurements reveal the presence of metamagnetic transition at 5 K and 2 K. Results of, ac and dc magnetization and isothermal remnant magnetization suggest a spin-glass like ordering below TN2. The heat capacity measurements show peaks corresponding to the magnetic ordering of Cr3+ and Tb3+ spins. The temperature variation of magnetic entropy change (-ΔSm) for different ΔH suggests the presence of the magnetocaloric effect in the vicinity of TN2. It is found that values of -ΔSm decreases with the increase in Mn-substitution. Present results have been understood in terms of modifications in magnetic exchange interactions introduced by the Mn-substitution at Cr-site.