Casey, a highly-touted rookie on tour this year, shot 69 Sunday to end at 14-under-par 274, one stroke better than the big German, who chased all the way, closing with consecutive birdies on his last two holes of the day.
For Casey, the win comes on just his eleventh start on the European Tour.
Paul Casey on his first win
In that short time, the 24-year-old Englishman had already amassed four top-20 finishes, including a runner-up showing at the Great North Open, when he was bettered by Andrew Coltart by one shot.
Now, he has a win.
This is only my 11th European Tour event, said Casey, so I still have a long way to go, and I hope to be here for a long time. Im looking at the big plan and that is to play in the best events in the world.
Should he keep up this kind of stellar golf, he will in time.
Casey moved to 26th on the Volvo Order of Merit Sunday with his winners check of 263,034 euro.
The goal is to get into the top-15 by the end of the year, he said, so I still have a lot to play for.
Coming down the stretch, it looked to be all wrapped up for the youngster following a birdie at the par-5 16th, which took him two shots ahead at 13-under.
Yet overnight leader and playing partner Cejka was not to be undone, and countered with a 25-footer for birdie at the next hole, the 17th, to move to within one.
He then hit a pitch-third to a mere six feet at the closing par-5 18th to set up another birdie.
With the pressure mounting, Casey responded, hitting a pitch of his own to within 10-feet of the cup.
When he got to the green, he analyzed the putt, and poured it in like a 10-year veteran for the outright win.
Just for sport, Cejka knocked his in as well, giving the match a stylistic conclusion.
I wasnt very solid today, but I was pleased that at least I managed to keep it interesting right to the end, Cejka said.
In outright third-place at 11-under was David Howell, who shot 70 and increased his Ryder Cup points standing to No. 24, up two from 26th.
Andrew Oldcorn also made a slight move for the week on the rankings list, replacing Andrew Coltart at the 13th slot.
No one got more out of the week than Casey, however.
Of his plans for the future:
I am already looking forward to next year and my focus is solely on Europe. Id like to play a couple of things in America, but the emphasis is still in Europe.
Full-field scores from the Gleneagles Scottish PGA Open