Growth is down to 13.5 percent from 29 percent the previous year.
Growth in the smartphone market slowed again in Q2 2015 after the Chinese market saw a drop in sales.
According to Gartner, worldwide sales totaled 330 million, an increase of 13.5 percent year-on-year from the 290 million unit sales in 2014.
Q2 2014 saw roughly 29 percent year-on-year growth, while Q2 2013 saw 46.5 percent year-on-year growth.
Disappointing results in China were responsible for the further slowdown, according to Anshul Gupta, research director at Gartner.
"China is the biggest country for smartphone sales, representing 30 per cent of total sales of smartphones in the second quarter of 2015," he said.
"China has reached saturation — its phone market is essentially driven by replacement, with fewer first-time buyers. Beyond the lower-end phone segment, the appeal of premium smartphones will be key for vendors to attract upgrades and to maintain or grow their market share in China."
Speaking to CBR, Gupta added:
"They’ve been driving the market in smartphone sales. China remained the driver, but smartphone penetration is high. Sales are almost stagnant compared to the same quarter year-on-year."
China saw smartphone sales fall year-over-year by 4 percent, the first decline in the market.
Among the other findings, Samsung saw its market share continue to decline, dropping from 26.2 percent to 21.9 percent.
"Samsung is struggling to grow sales past the 80 million mark," Gupta added.
Gupta suggested that Samsung’s high-end devices such as the S6 and S6 Edge would not be enough to drive growth.
"The iPhone 6 actually expanded the premium segment. Apple has beaten expectations of how big the premium segment could be.
"The premium segment has peaked. [Device vendors] need to look down for growth.
"In the short term, without a flagship phone soon they will continue to struggle."
Gupta said that he "expect(s) growth will come from the sub-$150 price point." He suggested that vendors should "focus on these markets and mid-tier to low mid-tier markets."
He added that "markets like Indonesia and India will see huge growth" and said that "vendors with global ambitions need to look at [for example] Thailand, India and Malaysia."