The demands declined as consumers stopped spending on nonessential products during the first quarter due to uncertainties brought on by the pandemic.
All of the top five smartphone vendors recorded a decline in the first quarter of 2020, except for Xiaomi which managed a surprise growth of 1.4 percent.
Strong sales of Redmi devices in international markets and aggressive online channel focus led Xiaomi to achieve better than expected sales, said the report titled "Market Share: PCs, Ultramobiles and Mobile Phones, All Countries, 1Q20 Update."
"The coronavirus pandemic caused the global smartphone market to experience its worst decline ever," Anshul Gupta, senior research analyst at Gartner, said in a statement.
"Most of the leading Chinese manufacturers and Apple were severely impacted by the temporary closures of their factories in China and reduced consumer spending due to the global shelter-in-place."
Although Samsung's smartphone sales declined 22.7 percent in the first quarter of 2020, the company still maintained the No. 1 spot with 18.5 per cent market share.
"Covid-19 negatively impacted Samsung's smartphone sales during the quarter. However, the decline could have been much worse," said Gupta.
"Its limited presence in China and the location of its manufacturing facilities outside of China prevented a steeper fall."
Huawei recorded the worst performance among the top five global smartphone vendors in the first quarter of 2020.
Sales of its smartphones fell to 42.5 million units, a decline of 27.3 percent year over year. Even with its first-ever decline in smartphone sales, Huawei held on to the No. 2 position with a 14.2 percent market share.
"Huawei will have a challenging year," said Gupta.
"It has developed the Huawei Mobile Service (HMS) ecosystem, but with the lack of popular Google apps and Google Play store, Huawei is unlikely to attract new smartphone buyers in international markets."
While Apple is not as dependent on China as Huawei, Oppo or Vivo are, it faced supply constraints and store closures which negatively impacted iPhone sales in the first quarter of 2020.
Apple's iPhone sales declined by 8.2 percent, totaling 41 million units in the first quarter of 2020.
Oppo's smartphone sales fell by 19.1 percent in the first quarter of 2020.
All other companies combined experienced a sales decline of 24.2 percent, according to Gartner.
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