Els, 43 became the oldest-ever winner of the event posting a last round three under par 69 to win by a shot on 18-under par.
Denmark's Thomas Bjorn, winner of the event 13 years ago, was left to count the costs of a 14th hole double bogey in signing for a score of 69 for an 18-under par total.
The win is Els' 68th worldwide and comes just four weeks before the defence of his British Open title at Muirfield where he will return on Tuesday for a practice round and a first visit since capturing the 2002 Open and the third of four Major victories.
"Winning this championship will just give me so much confidence going into the Open Championship," he said.
"Winning wire-to-wire means you have all the pressure of sleeping each night on the lead and with guys chasing you, so it's been quite a week for me as there was some really great players in the field."
"And for being the oldest winner, I was looking at the trophy and seeing Miguel Angel Jimenez's name there, and I guess given he's still only 49 he must have won it 10 years ago," he added, smiling.
"But it's just great to finally get my name on this wonderful trophy."
In fact, Els is five years older than the previous oldest winner in Zimbabwe's Mark McNulty who won the event in 1994.
Els, who also captured his first win of the year, intends taking a break from competition and while he's entered the Scottish Open, an event he won in 2000 and 2003, he hinted he may very well withdraw from the tournament at Castle Stuart.
Bjorn meanwhile has withdrawn from Monday's 36-hole (British) Open Championship qualifier at Walton Heath in Surrey to instead focus on next week's Irish Open at Carton House, and where he won the 2006 Irish Open when last staged at the course.
The Dane began the last round one shot behind Els and moved into the lead with three birdies in succession from the third hole.
However he came unstuck at the par four, 14th when forced to take a penalty drop after finding trees with his drive.
"I got off to the start I needed and got right in front, but the club that's been great this week has been the driver and it let me down on the back nine," he said.
"But when you go up against Ernie, you've got to take it 18 holes to the end and I didn't quite do it today.
"I've played a lot of golf with Ernie over the years, and he did all the stuff on Thursday with that score of 63 and he just hung in there from there and put in some solid rounds."
French rookie Alexander Levy carded a final day 71 to take third place at 16-under par and in the 22-year old's best Tour finish in just 14 appearances.
The 22-year old earned a prize cheque of €125 000 - the highest of his short pro career.
Three players - Germany's Martin Kaymer (69), Sweden's Alexander Noren (72) and Bernd Wiesberger (68) - shared fourth place on 15-under par.
Visiting American Dustin Johnson returns to the PGA Tour after a final round 66 for a share of 18th place at 12-under par.Leading final round scores at the European Tour's BMW International Open at the par-72 Golfclub Munchen Eichenried: (GBR and IRL unless stated, par 72):
270 - Ernie Els (RSA) 63 69 69 69
271 - Thomas Bjorn (DEN) 68 69 65 69
272 - Alexander Levy (FRA) 65 68 68 71
273 - Alexander Noren (SWE) 64 71 66 72, Martin Kaymer (GER) 64 71 69 69, Bernd
Wiesberger (AUT) 66 68 71 68
274 - Sergio Garcia (ESP) 71 69 65 69, Darren Fichardt (RSA) 70 66 69 69, Wen-yi
Huang (CHN) 71 69 69 65
275 - Robert Jan Derksen (NED) 64 72 70 69, John Parry 67 72 67 69, Joost Luiten
(NED) 69 68 67 71, Paul Waring 66 73 67 69, Brandon Stone (RSA) 66 71 67 71,
Marcel Siem (GER) 67 68 69 71, Peter Uihlein (USA) 70 66 67 72, Henrik Stenson
(SWE) 68 69 71 67
276 - Dustin Johnson (USA) 66 71 73 66, Ross Fisher 68 69 69 70, Matthew Baldwin
64 69 69 74, Danny Willett 69 65 70 72
277 - Matthew Nixon 65 71 70 71, Shane Lowry 69 69 74 65, Matteo Manassero (ITA)
68 69 71 69, Bernd Ritthammer (GER) 68 70 69 70