The Taiwanese firm, whose phones include the Butterfly, said net profit in the fourth quarter of 2012 had missed forecasts and plunged 91% year on year.
HTC's unaudited net profit for the October to December period was $34.47m (£21.47m), down from $379.84m (£236.67m) in the same period a year earlier and $134.44m (£83.72m) in the previous quarter.
HTC, the world's fifth-largest smartphone maker, did not elaborate.
Eighteen analysts had forecast a net profit of $50.67m (£31.55m) in the quarter, according to a Thomson Reuters survey.
Last week, market research firm Strategy Analytics predicted Samsung would continue to dominate the smartphone market.
It said there would be a clash between the South Korean firm and its US rival this year, with Apple trying to claw back the lower end of the market with a cheaper "iPhone mini".
Meanwhile, Sharp, which makes Aquos brand TVs among other products, is projecting an operating profit in the October-March second half of its business year.
That would unlock additional funds from banks, after the struggling Japanese company won a $4.4bn (£2.7bn) bailout from its lenders in October.
Company president Takashi Okuda said the firm had been benefiting from higher revenues from large household appliances and a slight upturn in LCD TV sales.
Sharp shares lost more than half their value in the 2012 calendar year against a 23% rise in the Nikkei index.
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