Tokyo's benchmark Nikkei 225 dropped 0.4 percent to 9,501.64, weighed down by the failure to bring Japan's stricken nuclear complex back from the edge of disaster.
The Fukushima Dai-ichi complex has been leaking radiation since it was severely damaged on March 11 following a mammoth earthquake and tsunami that decimated the country's northeastern coast.
Shares of Tokyo Electric Power Co. Inc., which operates the plant, have been in a tailspin since the disaster. On Monday, TEPCO shares lost 15 percent.
Japan's powerhouse auto industry still faces an uphill battle — with electricity supplies intermittent and key parts suppliers knocked out by the quake. Goldman Sachs estimated the shutdowns are costing the Japan automakers $200 million a day.
Shares in the major producers have been volatile as they try to restore production to pre-quake levels. Monday was bargain-hunting day, with Toyota Motor Corp. up 0.5 percent and Nissan soaring 4 percent.
Hong Kong's Hang Seng index was down 0.2 percent to 23,115.98 and Australia's S&P/ASX 200 was down 0.2 percent to 4,734.80.
Benchmarks in Singapore and Taiwan were also lower, while those in Shanghai and New Zealand rose.
South Korea's Kospi index was down 0.2 percent to 2,050.15, as sentiment among businesses drooped. According to the Yonhap news agency, the monthly Business Survey Index, a survey of the 600 largest businesses, came in at 99.3, a sharp drop from 113.5 of just a month ago. Readings under 100 mean pessimists outnumber optimists.
The military conflict in Libya, which brought oil production in the North African country to a standstill, was also weighing on sentiment. The Korea International Trade Association said last week that the country could lose more than $800 million in exports to Libya alone this year if the war continues until the end of the year.
Benchmark crude for May delivery was down 4 cents at $105.36 in electronic trading on the New York Mercantile Exchange.
In currencies, the dollar rose to 81.66 yen from 81.41 yen on Friday. The euro fell to $1.4064 from $1.4073.
