A method for preparing a functionalized polymer comprising the steps of preparing a pseudo-living polymer by polymerizing conjugated diene monomer with a lanthanide-based catalyst, and reacting the pseudo-living polymer with at least one functionalizing agent defined by the formula (I) ##STR00001## where A is a substituent that will undergo an addition reaction with a pseudo-living polymer, R.sup.1 is a divalent organic group, R.sup.2 is a monovalent organic group, and each R.sup.4, which may be the same or different, is a monovalent organic group or a substituent defined by --OR.sup.5 where R.sup.5 is a monovalent organic group, with the proviso that A, R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are substituents that will not protonate a pseudo-living polymer. Also, the functionalized polymer and a vulcanizable composition containing the polymer.