We report the existence of a Griffiths-like phase over a wide range of x due to the formation of nanosize ferromagnetic clusters in La 0.6Sr0.4Mn1-xCoxO3, the solid solution of ferromagnetic La0.6Sr0.4MnO3 and La0.6Sr0.4CoO3, from the magnetization measurements. In the studied compound, this phase arises due to the quenching of randomly distributed Co-O-Mn antiferromagnetic bonds in the ferromagnetic background. In contrary to the divalent alkaline-earth-doped manganites, the Griffiths-like phase in La0.6Sr0.4Mn1-xCo xO3 can exist entirely in the metallic state above T C (for x < 0.10). Based on the present study, a magnetoelectronic phase diagram is drawn. © 2013 American Chemical Society.