I just checked with the website where I buy ALL of my Mazda Accessories and they show the same part number, 0000-8D-N03, for the 2007 thru 2013 models. I emailed them to get a definite confirmation and they will respond to me by 10 or 11am tomorrow. It's actually a Mazda dealership located near Birmingham, Alabama (MedCenter Mazda) and they operate a website that sells Mazda OEM Accessories and (by request) most OEM parts at a significant discounts. I've been doing business with them for over seven years and I'm very pleased with their service, knowledge and prices. I'll post a confirmation here as soon as I hear from them tomorrow.
I have a 2012 CX-9 and I have the Rear Cargo Tray. I highly recommend it to all CX-9 owners. If you only buy one accessory, it should be the Cargo Tray! My CX-9 replaced a 2007 Ford Explorer (the worst vehicle I've ever owned, it had 134k miles on it and I had spent OVER $7k in repairs after the warranty expired....including a few things that had already been replaced one time under warranty....biggest POS in the world!)...sorry, my blood pressure jumps to stroke level at the very mention of that thing!!!
Anyway, in the Explorer you had to choose either a cargo mat that fit behind the 3rd row or one that fit behind the 2nd row with the 3rd row folded down. I got the larger one, which covered the folded 3rd row, but if I needed to raised the 3rd seatbacks I had to find a way to roll the mat up causing it to start tearing from the edges. When it was rolled or folded to raise the 3rd row, it blocked the rear window completely and rendered ethe cargo area behind the 3rd row completely useless!!!
The Mazda Cargo Tray for the CX-9 is very clever in comparison and I can't imagine why every other company with a 3-row SUV/CUV hasn't copied it! It's three separate pieces, one attaches to the each of the two 3rd row seat backs and the other covers the cargo area behind the 3rd row. When you fold down the 3rd row seats, there is a flap that expands to cover the gap that would exist otherwise and allow stuff to fall down into the cracks! I couldn't live without it! =)
I'll let you know when I get a definite answer on whether it will fit a 2013 model!