During the three months to August, the Windows Phone platform reached a market share of over 10 percent for the first time in France and Britain, with 10.8 percent and 12 percent respectively, the researcher said.
Nokia, which earlier this month agreed to sell its mobile phone handset business to Microsoft, is the main user of the Windows platform and the driver behind the increase.
"Windows Phone's latest wave of growth is being driven by Nokia's expansion into the low and mid-range market with the Lumia 520 and 620 handsets," said Kantar analyst Dominic Sunnebo.
"These models are hitting the sweet spot with 16 to 24 year-olds and 35 to 49 year-olds, two key groups that look for a balance of price and functionality in their smartphone."
Google's Android, which runs on Samsung and Sony smartphones among others, remained the leading platform in key European markets, which include Britain, Germany, France, Italy and Spain.
Android's market share increased to 70.1 percent from 68.8 percent in the same period last year. Apple's iOS was the second-biggest platform with a 16.1-percent market share, 2 percentage points more than last year.
BlackBerry, which earlier this month agreed to go private, saw its market share more than halved to 2.4 percent from 5.8 percent.
(Reporting by Harro ten Wolde; editing by David Evans)
