"Our data shows that Apple Watch is doing great and looks to be one of the most popular holiday gifts this year," wrote Cook in an email response to Reuters.
"Sales growth is off the charts. In fact, during the first week of holiday shopping, our sell-through of Apple Watch was greater than any week in the product's history. And as we expected, we're on track for the best quarter ever for Apple Watch," the executive continued.
Cook's comments were likely promoted due to a research report from IDC on Monday. It said Apple sold 1.1 million units of the Apple Watch during the third quarter of 2016, down 71 percent from the year-ago quarter. Apple hasn't disclosed specific sales numbers for the wearable.
IDC said Apple Watch's sale decline is in part to an aging lineup and an unintuitive user interface. Meanwhile, basic wearables like the Fitbit have gained popularity.
"It's still early days, but we're already seeing a notable shift in the market," said IDC Senior Research Analyst Jitesh Ubrani. "Where smartwatches were once expected to take the lead, basic wearables now reign supreme. Simplicity is a driving factor and this is well reflected in the top vendor list as four out of five offer a simple, dedicated fitness device. Meanwhile, from a design perspective, many devices are focusing on fashion first while allowing the technology to blend in with the background."