Nanoparticles of Zn_0.95-x Co_0.05InxO (x=0.0 to 0.07) were synthesized by the pyrolitic reaction of sol-gels obtained from respective metal precursors. X-ray diffraction and high-resolution transmission electron microscopy studies confirm the formation of impurity-free wurtzite type ZnO structure for all the compositions. While pristine ZnO is diamagnetic, Zn_0.95Co_0.05O nanoparticles show weak paramagnetic behavior at room temperature. When "In." is codoped with Co with x=0.0 to 0.07 in Zn_0.95-xCo_0.05InxO, a systematic increase in magnetic moment is observed up to x=0.07. First-principles modeling supports that the ferromagnetic phase become more favorable at higher indium doping concentrations.