The only son of Alexandru II Mircea and Ecaterina Salvaresso, he ascended to the throne after events characteristic for the decline in prestige of local custom and princely power under pressure from the Ottoman Empire (Wallachia's suzerain): Mihnea had to compete with a foreign pretender, the Lombard physician Rosso, who claimed to be descended from a Wallachian ruler,[1] and ultimately succeeded after enlisting the help of his grandmother, the influential Lady Chiajna.

[2] He, Ecaterina Salvaresso and Chiajna subsequently established what would become a highly unpopular rule, which followed the political guidelines imposed by Alexandru II, and saw a major increase in taxes — around 1583, the pressure was leading peasants to abandon their plots and flee to Transylvania in large numbers.

[4] A more powerful pretender was the real son of Pătrașcu cel Bun, Petru Cercel, who held the throne from 1583 to 1585, provoking Mihnea's exile to Tripoli (where he was kept in custody by Ottoman authorities).

The obligations he contracted in order to have Petru removed (around 700,000 scudi) forced Mihnea to increase the fiscal burden, and especially the quit-rent, to even higher levels upon his return to Bucharest.

Despite the established contacts, the Ottomans deposed Mihnea, in favor of Ștefan Surdul (who was allegedly a leather cutter and harness maker by trade).