ABO3 perovskite is a kind of very important functional material with versatile physical properties. Although B-site chemical substitution with various magnetic ions has been widely investigated, the A-site doping with magnetic transition metal is little known. Here we report AA3′B2B2′O12-type A- and B-site ordered ferrimagnet CaCu3Fe2Os2O12 with magnetic transition metals occupying three different atomic sites (A′, B, and B′ sites). This compound is synthesized by a special high-pressure annealing process. It possesses a much higher Curie temperature TC of 580 K compared with that of the B-site-only ordered Ca2FeOsO6 (TC=320K) without magnetic ion at the A site. First-principles numerical calculations reveal that this enhancement primarily originates from the additional spin interaction between the A′-site Cu2+ and the B′-site Os5+, generating a strong Cu2+(↑)Fe3+(↑)Os5+(↓) ferrimagnetic spin coupling. This work opens up an alternative way for enhancing the spin ordering temperature by introducing A-site magnetic ions.