Abstract: A process for preparing a functionalized polybutadiene is provided. The process comprises the following steps: a) homopolymerising butadiene with a catalytic system based on at least one preforming conjugated diene, a salt of one or more rare earth metals of an organic phosphoric acid, an aluminium-containing alkylating agent, an alkylaluminium halide; b) adding a polyfunctional compound to the pseudo-living elastomer formed in step (a); and c) adding a functionalizing agent to the mixture formed in step (b). The total molar amount of aluminium in the polymerization medium is such that the (aluminium/rare earth salt) molar ratio has a value between 1 and 5 and the polymerization is carried out at a temperature between 40° C. and 90° C. A functionalized polybutadiene that can be obtained by the process, and a rubber composition containing the functionalized polybutadiene is also provided.