The magnetic and magnetocaloric properties of CoMn0.9Fe0.1GeCoMn0.9Fe0.1Ge alloy has been investigated by using of electron microscopy, X-ray diffraction, calorimetric, heat capacity and magnetic measurements. The substitution of Fe atoms for Mn atoms in the CoMnGe system leads to a decrease in the martensitic transition temperature from 650 K to room temperature (RT) and presents the magnetostructural properties in vicinity of RT. In order to assess MCE, temperature dependent of magnetization measurements have performed under applying variable magnetic fields. The largest entropy change values are -34.9 J kg(-1) K-1 (magnetization) and -33.6 J kg(-1) K-1 (demagnetization) for Delta H=5T. The adiabatic temperature change value of CoMn0.9Fe0.1GeCoMn0.9Fe0.1Ge is calculated 8.5 K for 2 T from magnetic and heat capacity measurements. The density of states of electrons at Fermi level and the Debye temperature values of this alloy are found 1.19 states eV(-1) atom(-1) and 353 K from low temperature heat capacity measurements. This giant magnetocaloric effect makes this material a very promising candidate for future RT cooling applications. (C) 2015 Elsevier B.V. All rights reserved.