Off to the best start of his career, Nadal improved to 16-1 — including 13 wins in a row — on the year, having won two clay-court titles and been runner-up in another since returning from a left knee injury that idled him for seven months.
"It's very, very difficult to imagine something like this. But here we are today, and very happy about all what happened the last month, especially last three weeks," said Nadal, who beat No. 2 Roger Federer in straight sets in the quarterfinals.
"I don't have nothing to lose after seven months. I did much more than what I dreamed.''
It was Nadal's 12th straight win over Berdych, including seven consecutive on hard courts. Nadal will be seeking his third Indian Wells title in Sunday's final, where he'll play Juan Martin del Potro. The No. 7 seed del Potro fought back for a 4-6, 6-4, 6-4 win over top-ranked Novak Djokovic in the second semifinal. It was Djokovic's first loss since he fell to Sam Querrey on Halloween.
No. 2 seed Maria Sharapova and No. 8 Caroline Wozniacki will play for the women's title on Sunday.
''He looks strong again,'' Berdych said of Nadal, whose leg is taped just below his left knee. ''He still play very aggressive, and what he was missing in his first matches when he come back after the injury was maybe a bit of confidence in his game, but definitely not today and not anymore.''
Berdych came in with 18 match wins — second-most on tour this year — and was trying to make the final of three tournaments in a row for the first time in his career.
Berdych got broken at 5-all in the second set when he lost an easy smash in the sun, sending it wide.
Trailing 6-5, the sixth-seeded Czech held three break points, but couldn't convert. Twice Nadal came up with big serves and then Berdych committed an unforced error.
Berdych's netted forehand set up Nadal's first match point, but the fifth-seeded Spaniard pulled a forehand wide for deuce. Berdych sent a backhand into the net for Nadal's second match point, and he closed out the nearly 2-hour match in unseasonably hot temperatures when Berdych netted another backhand.
''I was very nervous at the end of the match to close the match and was lucky that my serve worked amazing in the last game in important moments,'' he said. ''Victories like today, like the other day, helps you a lot for the confidence and to remember all the things that you have to do in every moment.''
Nadal had 16 winners and 25 unforced errors but he saved 3 of 4 break points, getting broken in the eighth game on a double fault to give Berdych a 5-3 lead. Nadal then won the final three games of the match.
''When it was 5-3 since that time I serve only one first serve and he serve only one second serve,'' Berdych said. ''Actually, that was the difference.''