Economists polled by Reuters had forecast import prices slipping 0.3 percent after a previously reported 0.4 percent increase in February, when prices advanced for the first time after declining for seven straight months.
In the 12 months through March, prices plunged 10.5 percent, the largest drop since September 2009.
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Lower crude oil prices and a buoyant dollar have dampened price pressures, leaving inflation running well below the Fed's 2 percent target.
Officials at the central bank, some of whom have shown a willingness to consider a rate hike at the June policy-setting meeting, view the low inflation environment as transitory.
But the combination of low inflation and weak economic growth in the first quarter has prompted many economists to push back their rate hike expectations to later in the year.