Born in Milano, Lombardia but raised in region Liguria, Vallini studied in Turin. Later he traveled to Jamaica as a sailor. Later he returned to Turin where he continued studying and writing. In this period he also became friend with poet Guido Gozzano.

In 1907 he published his only two book of poems, Un giorno (A Day) and La rinunzia (The Renunciaton) in the style of Italian Crepuscolarian poetry.
In 1909 he graduated in Bologna and became school teacher in several Italian cities, he continued writing, publishing also Radda - Dramma lirico in un atto (1912), a play.
He also fought in the World War I and probably returned suffering with PTSD for the following years.

In 1920 he published his own translation of Oscar Wilde's Ballad of Reading Gaol. He died in the same year due to a sudden embolism.
His poetry was rediscovered during the 70s due to Italian poet and critic Edoardo Sanguineti who appreciated his poetry for being dark but also with a subtle irony and for being skeptically aristocratic.