His first accession to power was the result of a coup against his own brother, Giorgi III Dadiani, with whom he eventually reconciled in exchange of new estates.
His second term, after succeeding on the death of Giorgi III Dadiani, was consumed by wars with his in-laws, the prince of Guria and king of Imereti.
Giorgi Dadiani fled to Abkhazia and employed the Abkhaz-Circassian forces to reclaim the throne, but Gurieli's army successfully protected Mamia.
A subsequent peace deal brokered by the king restored Giorgi III Dadiani and granted to Mamia Sachilao, the former possessions of the Chiladze noble family, in fief.
[2][3] Mamia regained the government of Mingrelia after his brother's death in 1582, whereupon he instigated Gurieli to incarcerate the late Dadiani's underage son Levan.