He was the older brother of the statesman Piero Soderini, who was exiled at the return of the Medici in 1512; a third brother was Cardinal Francesco Soderini, bishop of Volterra. Like Piero he had been a pupil of Marsilio Ficino at his informal "academy", patronized by the Medici,Arnaldo Della Torre, Storia dell'Accademia platonica di Firenze 1902, p. 726; but for the often-cited "academy" see James Hankins, "The Myth of the Platonic Academy of Florence", Renaissance Quarterly 44.3 (Autumn 1991:429-475) which mentions both Soderini brothers. Soderini was a student rector at the Studio (the University of Florence) and was listed as an academicus in Coluccio Salutati's Declamations (453 note 80). but when Piero di Lorenzo de' Medici fled from Florence in 1494, he declared at once in favour of the revived Florentine republic and served as Florentine Ambassador to Venice. Philippe de Commines, unsympathetic to his policy, declared him, nevertheless, "one of the wisest statesmen in all Italy".Commines, The Memoirs of Philip de Commines, Lord of Argenton 1856, vol. ii, p. 141. On his return he was elected gonfaloniere of justice in 1497. The institution of a Grand Council in republican Florence, on the Venetian model, was largely on his initiative. As republican supporters of Savonarola and the populist party, he shared his brother's exile when the radical friar was arrested.
