The pact ensures the show, which is set in 1960s New York, will run for at least two more seasons, the series' fifth and sixth.
It also was announced Weiner has signed a new long-term deal with Lionsgate, extending into a possible seventh season.
The announcements were made by Charlie Collier, president of AMC, and Kevin Beggs, president of Lionsgate Television Group.
"I want to thank all of our wonderful fans for their support," Weiner said in a statement. "I also want to thank AMC and Lionsgate for agreeing to support the artistic freedom of myself, the cast and the crew so that we can continue to make the show exactly as we have from the beginning. I'm excited to get started on the next chapter of our story."
"We've been proud to support this show from the day we read Matt's ground-breaking pilot script and have loved building it with Matt and Lionsgate into the cultural phenomenon it has become," Collier said.