Before his appointment, Mamajonov served as deputy governor of Fergana region, head of the regional Department of Investments and Foreign Trade.

He graduated from the University of World Economy and Diplomacy in Uzbekistan and the Central Bohemia University in the Czech Republic. He also holds a Doctor of Business Administration degree from the European Institute of Applied Science and Management.

Throughout his career, Mamajonov has held positions at the Ministries of Justice and Foreign Affairs, as well as at Uzbekistan's embassy in Germany and its Consulate General in Frankfurt am Main.

In 2022–2023, he served as counselor for trade and economic affairs at Uzbekistan's embassy in China before being appointed first deputy head of the Ministry of Foreign Affairs' Department of Economic Diplomacy.

Mamajonov succeeds Rakhmatulla Nazarov, who served as Uzbekistan's ambassador to Belarus from 2024 to 2026.