Apple, which launched the Apple Watch in June, is within striking distance of leader Fitbit in the wearable devices market, market research firm IDC said.
Apple shipped 3.6 million Apple Watches in the second quarter of 2015, just behind Fitbit's 4.4 million wearable fitness and health trackers, IDC said.
The Apple Watch, which sports many health-related features and apps, is seen as the biggest rival to Fitbit's trackers.
Shipments of wearable devices more than tripled to 18.1 million units in the second quarter, IDC said.
"It's worth noting that Fitbit only sells basic wearables, a category that is expected to lose share over the next few years, leaving Apple poised to become the next market leader for all wearables," the IDC report said.
Fitbit's stock market listing in June got a rousing response from investors, with shares jumping as much as 60 percent. They closed at US$38.40 on Wednesday, nearly double their IPO price.
Reporting by Sai Sachin R in Bengaluru; Editing by Saumyadeb Chakrabarty