The decline was also the first since the Fukushima nuclear disaster, following a massive quake in 2011, drove purchases to successive records.
Thermal coal imports rose 1.7 percent to a record high 112.139 million tonnes, while crude oil imports climbed 2.9 percent to 3.42 million barrels per day (199.211 million kilolitres), customs-cleared data by the Ministry of Finance showed.
Japan, the world's fourth-biggest crude buyer, imported 4.17 million barrels per day (20.542 million kilolitres) of crude oil last month, up 15.9 percent, marking the second-straight month of gains, the data showed.
Japan's imports of liquefied natural gas totaled 8.149 million tonnes last month, up 0.1 percent from a year earlier. Imports of thermal coal for power generation declined 3.0 percent in March to 9.203 million tonnes, the data showed.
Following is a preliminary breakdown of energy imports for last month and 2015/16, with volumes of crude, oil products and gasoline/naphtha in million kilolitres; LNG, LPG and coal in million tonnes; values in million yen.