Tokyo's benchmark stock index dropped 2.44 percent early Monday after a plunge in New York, swept along in a global equities rout as worries about China's economy deepen.
The Nikkei 225 at the Tokyo Stock Exchange, which tumbled to its lowest close in over three months on Friday, fell 473.70 points to 18,962.13 in the first hour of trading.
The broader Topix index of all first-section shares dropped 2.67 percent, or 41.72 points, to 1,531.36.
Tokyo's poor start comes after New York shares plunged more than 3.0 percent Friday.
In its worst single session in nearly four years, the Dow Jones Industrial Average lost more than 500 points, or 3.12 percent, while the broader S&P 500 gave up 3.19 percent and the Nasdaq Composite shed 3.52 percent.
Jitters over China and the global economy saw traders move into the yen -- a safe haven in times of turmoil and uncertainty -- which is a negative for Tokyo equities as it hurts the profitability of Japanese exporters.
On currency markets, the dollar dropped to 121.82 yen, compared with 122.06 yen on Friday in New York. The unit was above 124 yen on Thursday in Asia.
The euro was $1.1376 and 138.54 yen, weakening from $1.1386 and 138.97 yen.
Investor jitters have spiked on concerns China is slowing more than previously thought after the central bank devalued the yuan in a shock move seen as a bid to boost sagging exports.
Equities worldwide have lost more than $5 trillion in value since the cut on August 11, which also spurred a slump in emerging-market currencies and commodities.
"Things are probably going to get worse before they get better," Nader Naeimi, Sydney-based head of dynamic asset allocation at AMP Capital Investors, told Bloomberg News.
"You really need rate cuts and more policy easing in China. In the meantime, things can get worse. We've got to see more clarity around the Fed" and its timeline for raising interest rates, he added.
The US Federal Reserve voiced caution over China as a concern in the minutes of its last meeting, which lowered expectations that the central bank could lift rates as early as next month.