Imports rose an annual 3.4 percent versus forecasts for a 0.8 percent rise, while the trade balance stood at a deficit of 808.9 billion yen ($7.98 billion), much larger than expectations for a 646 billion yen deficit.
Japan's trade balance has been in a deficit for 22 months in a row now.
"The data was not really a surprise at all. They [Japan's policy makers] were hoping for a lower yen to stimulate exports and a lower yen just isn't coming," said Boris Schlossberg, managing director at BK Asset Management.
"The problem is that the unbelievable decline in U.S. rates that has kept dollar-yen much lower than what everybody thought. It's frustrating all the plans of [BOJ Governor Haruhiko] Kuroda and [Prime Minister] Shinzo Abe to stimulate the economy," he said.
The Bank of Japan ends a two-day meeting on Wednesday and is expected to maintain its current monetary policy, under which it plans to increase Japan's base money by 60-70 trillion yen ($589-$688 billion) a year via aggressive asset purchases.
"The Bank of Japan hasn't done enough. They need to do at least a 100 trillion yen to drive dollar-yen to 105 and stimulate the economy," Schlossberg added.