Green Party MP Mehmet Kaplan was ordered to leave minutes after his plane landed in Israel because he had "failed to follow procedure" and obtain an entry visa in Sweden, ministry spokeswoman Sabine Hadad told AFP.
Dror Feiler, an Israeli artist based in Sweden who has relinquished his Israeli citizenship, was also expelled upon arrival at Ben Gurion airport in Tel Aviv, Hadad said.
The pair had been detained after Israeli commandos on May 31st intercepted an aid flotilla bound for the blockaded Gaza Strip and nine Turkish activists were killed when commandos raided the flagship, the ferry Mavi Marmara.
Passengers detained in the raid on the flotilla were later released after signing a letter "in which they pledged to obtain authorisation to enter Israel from Israeli embassies in their respective countries," Hadad said.
"They [Kaplan and Feiler] were perfectly aware of these dispositions, but they did not respect them," she said, explaining why the pair were barred from entering Israel on Sunday.
Northern Irish Nobel peace laureate and activist Mairead Maguire was deported from Israel in June because she had also tried to reach Gaza by boat in defiance of Israel's naval blockade.
In October, the Israeli supreme court rejected Maguire's appeal against a court decision ordering her deportation.
She was one of 19 activists on board the Irish-owned "Rachel Corrie," which tried and failed to reach the Gaza enclave in early June.
Corrie was an American member of the International Solidarity Movement who was crushed to death in the Gaza Strip in 2003 by an Israel Defence Forces bulldozer while acting as a human shield in front of a local Palestinian's home in an attempt to prevent its demolition by IDF forces.