Boland, who is a minister in the coalition Social Democrat/Green government, was approved in a vote by a majority of party members meeting in their annual congress at the weekend. He saw off competition from the more left-orientated candidate Magnus Wåhlin.
"I am fantastically happy and proud and honoured that my party has chosen me for the finest job one can have," he told media.
Instead of one party leader, the Green Party shares the role between two spokespersons, one male, one female.
After a poor result at the general election last autumn, the Green Party is aiming to bounce back in this month's EU elections, where it traditionally outperforms its domestic results.