The Dane stormed home with a final round 6-under-par 66 to finish with a 272 17-under-par total and win by a shot from Italys Veronica Zorzi.
It was Tinnings fourth victory on the Robe di Kappa Ladies European Tour after she won the Open de Espaa Femenino Castelln Panormica Golf &Country Club three weeks ago.
Tacking a second consecutive round of 66 onto opening rounds of 69 and 70, Tinning did just enough to claim the prize winnings as she fended off a strong challenge from Zorzi.
The darling of the Italian galleries had an eagle three at the last to take her to 16 under par playing in the penultimate group.
But it wasnt enough to fend off Tinning, who only needed to par the last hole for her victory.
Zorzi fired a final-round 66 to finish alone in second position whilst fellow Italian Sophie Sandolo and New Zealander Lynnette Brooky also carded 66. They shared third position on 15 under par.
Tinning, who also won the Ladies Italian Open in 2002, as well as the Irish Open in the same year, said: I am so happy about this win especially because it was so close out there. You had to play your best to win. I couldnt have played any better.
It means quite a lot. I won the Italian Open before and I like Italy and I like Rome. I think its a great place and I liked the back nine a lot better.
After seeing Zorzi make that three on the last, that made it tougher but then again, its a par 5 and I made my par so Im very delighted.
Tinning remains at the top of the LET Money list and third in The 2005 Solheim Cup points table. There are seven places available for automatic selection.
Im definitely looking forward to The Solheim Cup and I feel quite comfortable now. I thought that I would need to play well in July and August but it looks like I already have done so thats not bad, is it? said Tinning.
She spent the majority of last year playing in America but after a tough time, this year she is competing in Europe.
I was struggling last year on the LPGA but I think I just got a lot stronger mentally, she said.