It depends on the condition, if it's stiff and not pliabble, probably not work. There has been some info posted a while back her on HR about the best method to clean and take care of leather . I don't know if you can bring back stiff leather, My wife and I haven't owned any horses for several years, but we still have our saddles, I try to use Neatsfoot oil every year, probably not the best for upholstery. My son picked up a couple free leather sofa's from CR to do the interior of his 22 dodge lakester, he wants the just out of the barn look.
good quality Furniture will have leather on the back, never sat on, and No vinyl used on sides or back.