The show began the second half of Season 3 Sunday night.
In addition to the 9 p.m. premiere, the show encored at 11 p.m., midnight and 2 a.m., delivering a total of 16.6 million viewers for the night, the cable network said.
The previous ratings high for the Andrew Lincoln-Norman Reedus show was 10.9 million viewers for the Season 3 premiere Oct. 14, 2012.
"When you look at numbers like this, the first thing that comes to mind is how grateful we are to the fans of this show. They embrace 'The Walking Dead' in a way that we wanted to believe was possible but we never take for granted," Charlie Collier, AMC's president, said in a statement Monday. "The cast and crew put everything they have into making this show. They're a phenomenally talented group who truly give their all. We congratulate everyone involved."