Local media report that Fikrat Sadyqov was released on condition that he notify police before traveling outside the capital of Baku.
The National Security Ministry did not explain its decision to release Sadyqov, the former head of the state-owned chemical company Azerkimiya.
But a spokesman for the ministry said an investigation is continuing.
Sadyqov was detained in late October on charges of plotting to overthrow the government together with other top officials.
Earlier this month, Azerbaijani authorities released another alleged coup plotter.
Eldar Salayev, a former president of the Azerbaijani Academy of Sciences, was reportedly released for health reasons but charges against him were not dropped.
(RFE/RL's Azerbaijan Service/Turan)
The National Security Ministry did not explain its decision to release Sadyqov, the former head of the state-owned chemical company Azerkimiya.
But a spokesman for the ministry said an investigation is continuing.
Sadyqov was detained in late October on charges of plotting to overthrow the government together with other top officials.
Earlier this month, Azerbaijani authorities released another alleged coup plotter.
Eldar Salayev, a former president of the Azerbaijani Academy of Sciences, was reportedly released for health reasons but charges against him were not dropped.
(RFE/RL's Azerbaijan Service/Turan)