The Taiwanese container line posted a net loss of NT$9.4bn ($319.21m) last year as against a net profit of NT$11.79bn in 2010.
Revenue slipped to NT$98.03bn compared to NT$111.92bn a year ago, the company announced to the Taipei stock exchange.
Earnings were trimmed by higher operating costs at NT$107.53bn, rising from NT$96.67bn in the previous year.
Yang Ming said last month that it was delaying the taking over of five 4,500 teu containerships from Taiwan's state shipbuilder CSBC. Yang Ming would prefer the vessel deliveries to be delayed by between 10 to 16 months, indicating signs of overcapacity in the box shipping sector.