The 26-year-old from Chateroux defeated three other players by a one stroke margin at 12-under-par 207 (70-69-68), with a clinch birdie putt at the final hole.
Gwladys Nocera from France, Spaniard Paula Marti and Italian Sophie Sandolo finished in a tie for second position at 11-under-par 206.
Nocera carded rounds of (68-71-69) for her third runner-up spot of the season, after she finished in second position at the Thailand Ladies Open and the Siemens Austrian Ladies Golf Open earlier in the year.
Marti, playing in the final group with Icher and Sandolo, carded rounds of (68-70-70) and just missed out on the chance to force a play off after leaving her birdie putt short at the 18th hole.
Sandolo, the second round leader, fired rounds of (69-68-71) to equal her best finish on the LET, after she secured another second place finish at the Ladies Spanish Open in 2003.
New Zealander Lynnette Brooky rounded off her season in fifth place totalling 10-under par with rounds of (71-70-68).
Anja Monke and Miriam Nagl of Germany both tied for sixth position with Denmarks Iben Tinning, the 2005 Money List winner, at 9-under-par 210. Tullia Calzavara from Italy and Asa Gottmo tied for ninth position at 8-under-par.
Spanish 15-year-old amateur sensation Carlota Ciganda totalled 7-under-par 212. Ciganda fired a course record 8-under-par 65 in the final round to tie for eleventh position with Trish Johnson and Stephanie Arricau.
Icher, who is based in Orlando, Florida, earns 34,000 in prize money as well as a scooter courtesy of Yamaha for her victory.
She also becomes the fourth player to successfully defend her own title this year on the LET.
I feel more confident with my putting now under pressure, said Icher. This win will give me more confidence when I return to America.
It seems that Spain is very lucky for me because Ive now won here three times on the LET.
On top of her two Catalonia Ladies Masters titles, Icher also won the Ladies Spanish Open in 2002, as well as the German Open and Mexx Sport Opens in 2001.