Mankell, the author of the popular Wallander series of detective novels, will be among a total of 20 Swedish participants in the "Freedom Flotilla 2," Ship to Gaza Sweden said in a statement.
"Interest in participating in the Freedom Flotilla has been enormous and we have been forced to turn down many people who wanted to show their solidarity with practical actions," the organisers said, providing the names of eight of the Swedes scheduled to take part.
The Swedes, who also include a parliamentarian and a midwife, will be among the "thousands" of pro-Palestinian activists from around the world set to participate in the convoy, the statement said.
Mankell was one of 11 Swedes who participated in last year's aid flotilla of six ships carrying 682 people from 42 countries that headed for Gaza despite warnings from Israel, which is blockading the Hamas-ruled Palestinian territory.
Israeli marines swarmed aboard the Turkish flagship of the flotilla bound for Gaza, killing nine Turks in international waters and plunging ties with Ankara into deep crisis.
Upon his return to Sweden after that ordeal, Mankell charged that "all the ships (in the flotilla) were hijacked, and this was really piracy."
"What will happen next year when we come back with hundreds of boats? Will (Israel) fire a nuclear bomb?" he asked.