That beats out iOS devices which accounted 38% of mobile ad traffic over the same period.
But iOS devices still dominate in revenue at 52% verus 33% for Android. The good news for Android though is it’s heading in the right direction.
"Although still trailing iOS in terms of monetization, Android is making slow advancement in that category, as well," the Opera Mediaworks report said, noting that in the same quarter last year Android accounted for only 27% of revenue.
Still, most of Android's gain has been at the expense of BlackBerry and Symbian devices, not iPad or iPhone.
The report said Samsung was the "clear leader" in the Android market, accounting for more that 60% of ad impressions on Android (LG is far back in second at 11%).
Of the 38% of mobile ad traffic that ends up on iOS devices, 25% goes to iPhones, 10% to iPads, and three percent to iPod Touch devices. The difference is much more dramatic for Android where 41% of its share of ad traffic is on phones, and only 1.5% on tablets.