Alauddin was a nephew and a son-in-law of his predecessor Jalaluddin. When Jalaluddin became the Sultan of Delhi after deposing the Mamluks, Alauddin was given the position of Amir-i-Tuzuk (equivalent to master of ceremonies). Alauddin obtained the governorship of Kara in 1291 after suppressing a revolt against Jalaluddin, and the governorship of Awadh in 1296 after a profitable raid on Bhilsa. In 1296, Alauddin raided Devagiri, and acquired loot to stage a successful revolt against Jalaluddin. After killing Jalaluddin, he consolidated his power in Delhi, and subjugated Jalaluddin's sons in Multan.
Over the next few years, Alauddin successfully fended off the Mongol invasions from the Chagatai Khanate, at Jaran-Manjur (1297–1298), Sivistan (1298), Kili (1299), Delhi (1303), and Amroha (1305). In 1306, his forces achieved a decisive victory against the Mongols near the Ravi riverbank, and later ransacked the Mongol territories in present-day Afghanistan. The military commanders that successfully led his army against the Mongols include Zafar Khan, Ulugh Khan, and his slave-general Malik Kafur.
Alauddin conquered the kingdoms of Gujarat (raided in 1299 and annexed in 1304), Ranthambore (1301), Chittor (1303), Malwa (1305), Siwana (1308), and Jalore (1311). These victories ended several Hindu dynasties, including the Paramaras, the Vaghelas, the Chahamanas of Ranastambhapura and Jalore, the Rawal branch of the Guhilas, and possibly the Yajvapalas. His slave-general Malik Kafur led multiple campaigns to the south of the Vindhyas, obtaining a considerable amount of wealth from Devagiri (1308), Warangal (1310) and Dwarasamudra (1311). These victories forced the Yadava king Ramachandra, the Kakatiya king Prataparudra, and the Hoysala king Ballala III to become Alauddin's tributaries. Kafur also raided the Pandya kingdom (1311), obtaining much treasure and many elephants and horses.
During the last years of his life, Alauddin suffered from an illness, and relied on Malik Kafur to handle the administration. After his death in 1316, Malik Kafur appointed Shihabuddin, son of Alauddin and his Hindu wife Jhatyapali, as a puppet monarch. However, his elder son Qutbuddin Mubarak Shah seized the power shortly after his death.