The former Laguna Beach star shot to fame on the MTV series but exited last year following five seasons. She was replaced as narrator by Kristin Cavallari.
Speaking on Ryan Seacrest's KIIS-FM radio show, creator Adam DiVello said that Conrad and fellow castmate Whitney Port - who departed to front her own series The City - will be present at the one-hour special to mark the final ever episode of the show and the season finale of The City.
"Lauren Conrad will be at the finale event along with Whitney Port and the whole entire cast," he said. "It will be a big party."
He went on to tease that fans can expect an "exciting ending" to the show, and revealed that not even the cast know exactly how it will bow out.
"We have some stories being paid off in the finale that I think the viewers will find pretty exciting," he epxlained. "Everybody's coming to peace with the stories we've been following.. I think a few of them definitely found happiness and what they were looking for."
He added: "It will be an exciting ending. We definitely have a couple of surprises up our sleeve that the cast don't even know about!"
Conrad previously ruled out the possibility of appearing in the final episode of the series, insisting that she is happy about how her departure was played out on screen.
The final ever episode of The Hills airs July 13 on MTV.