Mamadou Tandja was born in 1938 in Maine-Soroa, in southeastern Niger near the country's border with Chad. He belongs to the ethnic minority Kanouri community. Attending military schools in Madagascar and Mali, he joined the army in the mid-1950s, rising to the rank of colonel. In 1974, Tandja participated in the military coup that ousted Niger's first post-independence president, Hamani Diori, and brought General Seyni Kountché to power. During the Kountché regime, Tandja served as prefect of the Tahoua and Maradi regions, ambassador to Nigeria, and two-term minister of the interior. In addition to carrying out the duties of his political posts, Tandja also served as commander of several army garrisons. He was known for hard work and efficiency, winning the nickname " the working chief." His reputation, however, was marred by his role, as interior minister, in the violent repression of activities by Tuareg rebels in the north in 1990. During the massacre, Nigerien troops shot dead 63 Tuareg protestors and sparked five years of rebellion in the northern part of the country.
An asset declaration made upon Tandja's election to the presidency showed him to be a substantial property owner, with large livestock holdings. Tandja has ten children.