This gave Apple 25.8% market share in a quarter which saw a total of 49.6 million units shipped.
IDC's figures showed that wrist-worn wearables comprised 63.2% of the units shipped, ear-worn devices showed faster growth - 135.1% year-on-year.
Xiaomi was second in the listings, with its Mi Band largely responsible for 6.6 million unit shipments and a share of 13.3%.
"The elimination of headphone jacks and the increased usage of smart assistants both inside and outside the home have been driving factors in the growth of ear-worn wearables," said Jitesh Ubrani research manager for IDC Mobile Device Trackers.
"Looking ahead, this will become an increasingly important category as major platform and device makers use ear-worn devices as an on-ramp to entice consumers into an ecosystem of wearable devices that complement the smartphone but also offer the ability to leave the phone behind when necessary."
"Shipments of wristwear – including watches and wristbands – grew 31.6% year over year, and continue to dominate the wearables landscape," said Ramon Llamas, research director for Wearables.
"While the functionalities and capabilities have grown and changed, the one common thread is the relentless focus on health and fitness.
"This has resonated strongly with users and health insurance companies alike, and new health and fitness insights attract a larger audience."