Marino Keith's own goal just before the interval condemned the Pilgrims to their first reversal at Home Park since September last year - their only defeat as they claimed the Second Division title.
Keith headed Leeds' skipper Paul Butler's lofted right-wing cross into his own net as Argyle struggled to clear their lines following a spell of sustained pressure from their visitors.
Keith had an almost immediate chance to restore parity before half-time but Leeds goalkeeper Neil Sullivan reacted smartly to turn away his shot after Clarke Carlisle's mistake.
Leeds, unchanged from the side that had beaten Coventry three dayspreviously, had few moments of concern in the second period, with Argyle's best chance falling to Lee Hodges deep into injury-time.
His drive, though, was easily tipped over the crossbar by Sullivan.
Sullivan's Argyle counterpart, Romain Larrieu, recalled for the first time in more than a year, was also in fine form.
He made two world class saves to deny Brain Deane's point-blank shot in the first half, and turn away Leeds substitute Matt Spring's deflected rising drive in the second.
After a dream start to life in the Coca-Cola Championship which they briefly led, Argyle now have a clear indication of the task ahead of them.
Plymouth: Larrieu, Connolly, Wotton, Coughlan, Gilbert, Norris (Milne 79), Friio, Makel, Capaldi (Hodges 24), Evans (Crawford 71), Keith.
Subs Not Used: Lasley, Adams.
Booked: Friio.
Leeds: Sullivan, Kelly, Carlisle, Butler, Crainey, Richardson, Wright, Walton (Spring 66), Pugh, Deane (Ricketts 82), Joachim (McMaster 82).
Subs Not Used: Carson, Duberry.
Booked: McMaster.
Goals: Keith 43 og.