El Khayati was already committed for next season under the terms of the deal he signed in January after Albion took up an option to keep him.
However, the 26-year-old Dutchman will now remain at the Pirelli Stadium until the summer of 2017.
“Nasser became a very important part of the group last season and we are delighted that a new contract has been signed,” said Burton assistant manager David Oldfield.
“We are looking forward to him being as effective for us as he was last season.
“Nasser has great individual skills and was an important member of a successful group.”
El Khayati was signed from Dutch club Kozakken Boys in January and had an increasing impact as the season progressed, making 18 appearances as Albion secured the League Two title.