The NBC legal drama stars Kathy Bates as unconventional lawyer Harriet 'Harry' Korn.
"[The network is] liking their pilot development a lot, [which] doesn't speak well for us." Kelley told the Los Angeles Times.
Harry's Law currently attracts an average of just under 9m viewers, but Kelley suggested that the show could be dropped because it does not appeal to younger viewers.
"Word seems to be out that we're a show for old people," he joked. "If we could just more get younger viewers and keep some of our regular viewers from dying we'd be feeling better."
However, the writer admitted that he has enjoyed the creative freedom that NBC has allowed him on the show.
"They kind of let us do what we do," he explained. "If it were one of their more cherished commodities, they might micromanage us more."
NBC recently picked up a number of pilots to series, including Jimmy Fallon's Guys With Kids, Anne Heche's Save Me, White House comedy 1600 Penn and vet sitcom Animal Practice.
Glee co-creator Ryan Murphy's show The New Normal and Matthew Perry sports comedy Go On have also been given the green light.