The research firm said global tablet shipments reached 52.9 million units, up just six percent from the same period a year ago.
Growth was led by devices using the Google Android operating system.
Android tablet sales rose 11 percent to 36.8 million in the March-June period, the survey found, and grabbed a 70 percent market share.
Apple sales fell from a year earlier to 13.3 million, according to Strategy Analytics' figures which were above Apple's own report this week showing 12.3 million.
The research firm said Apple's market share slipped to 25 percent based on the latest decline.
(Also see: Tablets to Outsell PCs by 2015: Gartner)
Windows-powered tablets accounted for five percent of the market, with unit sales up some 28 percent at 2.7 million, the survey found.
"Android consolidation continued as it was the chosen OS (operating system) for seven out of 10 tablets shipped in the market," says Strategy Analytics researcher Peter King.
"Android is continuing to make steady progress due to the wide range of vendors and wide range of screen sizes and price-points."
(Also see: Global Device Sales Shifting to Mobile: Gartner)
Several analysts have said the tablet market has become saturated in many developed countries and that large-screen smartphones or "phablets" are often being used instead.