Apple did not immediately respond to CNBC's request to confirm the report. But the data echo a report from JPMorgan, who earlier this summer slashed its Apple Watch estimates for fiscal 2016.
If true, the drop in Apple Watch shipments reported by IDC could leave growth muted for the rest of 2016, Jitesh Ubrani, senior research analyst at IDC Mobile Device Trackers, said in a release.
"Consumers have held off on smartwatch purchases since early 2016 in anticipation of a hardware refresh, and improvements in WatchOS are not expected until later this year, effectively stalling existing Apple Watch sales," Ubrani said. "Apple still maintains a significant lead in the market and unfortunately a decline for Apple leads to a decline in the entire market."
Apple was the only top vendor in the data to see yearly declines, with Samsung and Lenovo both having 50 percent positive growth or more, according to IDC, a global market research firm that focuses on the technology industry.
Still, to be fair, IDC said it tracked data in comparison to the initial launch of the Apple Watch, "which is in many ways the same product offered in the most recent quarter with price reductions."
It comes as traditional watchmakers are increasingly coming online, amid rumors of a new Apple Watch as soon as September. In the mean time, Apple's investors are watching the company closely ahead of next week's earnings, which are expected to reveal whether iPhone sales can continue to grow at their previous pace.
If iPhone sales growth slows, it could push the company to bolster other revenue streams, like watches. Still, in last quarter's earnings, those "other products," watch included, did turn out to be a bright spot.
Apple shares were down slightly Thursday afternoon, in line with the broader market.