Due to the expensive and unsuccessful wars, repeated Mongol raids, and economic instability, the government was faced with a revolt in 1277. The Uprising of Ivaylo was a rebellion of the Bulgarian peasantry against the incompetent rule of Emperor Constantine Tikh and the Bulgarian nobility. The revolt was fuelled mainly by the failure of the central authorities to confront the Mongol menace in north-eastern Bulgaria. The Mongols had looted and ravaged the Bulgarian population for decades, especially in the region of Dobrudzha. The weakness of the state institutions was due to the accelerating feudalisation of the Second Bulgarian Empire.

The peasants' leader Ivaylo, said to have been a swineherd by the contemporary Byzantine chroniclers, proved to be a successful general and charismatic leader. In the first months of the rebellion, he defeated the Mongols and the emperor's armies, personally slaying Constantine Tikh in battle. Later, he made a triumphant entry in the capital Tarnovo, married Maria Palaiologina Kantakouzene, the emperor's widow, and forced the nobility to recognize him as emperor of Bulgaria.