Tokyo Customs stopped imports of 26,697 electric appliances between January and June this year, citing copyright infringement, officials said.
The number has reached a new all time high for the fourth year in a row.
They added that many of the items are modeled after genuine products manufactured by Apple Inc. and other big-name companies, including earphones, charging cables and other items.
An increasing number of people buy smartphones as fashion items, as they become more widely available, an official said.
Intellectual property rights are not allowed in import or export of goods infringing intellectual property rights.
In the first half of this year, Tokyo Customs suspended imports of 114,376 items.
Electric appliances increased by about 6,000 pieces from the same period a year ago, making up the largest category at 23.3 percent.
Clothes accounted for the second largest category with 13,774 items 12 percent, while bags made up the third largest category with 11,558 items 10.1 percent China topped the list with 48,591 items, down 33 percent from the same period the previous year.
Hong Kong was second with 31,639 items, an increase of 298.2 percent, followed by Vietnam with 25,214 items, up by 65 percent.
1,479 items from the Philippines were suspended from import, down by 82.4 percent.
It is hard to distinguish genuine items from counterfeit products sold at online stores.
Starting from October, tougher measures against illegal copies will be introduced at points of entry into Japan.
Site users have to negotiate with operators when they are confiscated because customs officials are unable to handle refunds.
Don't be fooled, said Koji Toyama, director of the Customs Clearance Division at Tokyo Customs.