The fourth season of the American political drama series Madam Secretary premiered on October 8, 2017, on CBS in the United States. It is produced by CBS Television Studios, and Revelations Entertainment with series creator Barbara Hall serving as executive producer, alongside Morgan Freeman, Lori McCreary, and Tracy Mercer.

When does the season for madam secretary start? Okie... think carefully first, then make a decision:
The relevant sentence in the passage is: The fourth season of the American political drama series Madam Secretary premiered on October 8, 2017, on CBS in the United States. So, the answer is October 8 , 2017.