First of all, a very Happy Birthday to two-time Grammy Award winner Mr. Mraz, who turns 43 today!
Jason has penned several hits, but "I'm Yours" is probably his best known song.
Opening Riff
The intro has a laid back, summery vibe thanks largely to the double slides:
The palm-muted, off beat second guitar part also helps to give it that tropical feel. But if you want to get close to the original sound, you'll need to de-tune your guitar!
Original Tuning for "I'm Yours"
For this song, Jason uses what is actually a very unusual tuning. The three bass strings (usually tuned E, A, and D) are each tuned a whole tone lower. That gives us the following:
6th string: D
5th string: G
4th string: C
3rd string: G
2nd string: B
1st string: E
He then adds a capo to the 4th fret.
The D-G-C-G-B-E tuning means that all our chord shapes have to change. On the plus side, strings 1, 2, and 3 are unaffected, so the riff you learned above works perfectly with this tuning too.
OK, so here are the shapes you'll need in the D-G-C-G-B-E tuning:
Here's a video of Jason performing the song and using the tuning and shapes you've just learned. Enjoy!