The Rams suffered successive 3-0 defeats away to Nottingham Forest and Brentford prior to the international break but, despite a bright start at Pride Park, Derby could not end its winless run in the league, which has now been extended to six games.
Derby took the lead in the sixth minute, left-back Scott Malone on hand to tuck in from close range after Martyn Waghorn kept the play alive after Alex Smithies' save from Tom Huddlestone's strike.
With Derby on top, Waghorn's seemingly valid penalty appeals fell on deaf ears in the 16th minute, and the home side's frustrations were compounded moments later when Richard Keogh hauled down Glatzel, who opened his Cardiff account from the resulting spot-kick.
Jack Marriott rattled the crossbar three minutes after the restart as Derby swiftly came out of the blocks, while Waghorn flashed a strike wide.
Kelle Roos's error gifted Glatzel an opportunity to double his tally late on but Matthew Clarke made a goal-saving clearance to secure a point as Cocu's wait for a first home win rumbles on.