Ward, who is capable of playing at hooker or flanker, has made 115 appearances for the club since signing from Cornish Pirates in 2012.
Details of the length of the 31-year-old's new deal have not been disclosed.
"I am absolutely delighted that Dave has significantly extended his length of contract with Harlequins," director of rugby John Kingston said.
"Dave is flexible in that he can play both hooker and back row, but in addition to that, he is also a magnificent leader who sets a shining example to others."
Versatile Harlequins forward Dave Ward has signed a contract extension with the Premiership club.