[1][2] Son of Giuseppe Tajani and Teresina Fattizza, he graduated in law in 1850 and practiced as a lawyer; in 1858, he agreed to take on the defense of Giovanni Nicotera and the other survivors of the Sapri expedition, managing to reduce their sentences.

In 1859, he volunteered in the Second Italian War of Independence, initially as a private soldier, before being promoted to military auditor with the rank of colonel.

[6][7] Tajani made rapid progress in his career after the unification of Italy, becoming general prosecutor of the Court of Appeal of Catanzaro from 1867 to 1869, and of that of Palermo from 1867 to 1871.

[8][9] Elected deputy in 1874 for the constituency of Amalfi for the historical Left, he was Minister of Justice in the two-year period 1878 - 1879 and again from 1885 to 1887 in the Depretis cabinets.

[2] While serving as a politician Tajani took part in numerous trials: in 1875 he defended it:Raffaele Sonzogno in the trial against Giuseppe Luciani; in 1878 he defended Francesco Crispi, accused of bigamy;[11] in 1879 he obtained sovereign pardon for Giovanni Passannante Umberto I's would-be assassin, and finally he dealt with the divorce of Giuseppe Garibaldi from Countess it:Giuseppina Raimondi.