All I know for sure is that The Mentalist’s original music is credit to American composer, Blake Neely. In his studio’s site, he has a page dedicated to his favorite cues from the show (with streaming samples), and track #1 entitled “Believe,” is labeled “Theme from The Mentalist.” However, it is not the one used in the short intro of the series—the one where they show several definitions of “mentalist.”
It (intro song) actually sounds more like track #11 EP 103: Sand Castle, again from this page.
Additional
The Mentalist is just about to start its second season on September 24, 2009. It airs Thursdays 10 p.m. on CBS, and stars Simon Baker, Robin Tunney, Tim Kang, Owain Yeoman and the very hot Amanda Righetti.
Watch & Listen
Below is that very short sequence people consider the “intro” to The Mentalist.