Helsinki district court said it had sentenced the lead writer of a report, published in 2017 and entitled "Finland's most secret place", to pay a fine while another journalist was sentenced but left without a punishment due to her minor role in the reporting.
Finland has for years been among the top countries in a global press freedom ranking published by Reporters Without Borders, but last year slipped to fifth place, partly due to the court case.
"In an article published in Helsingin Sanomat on 16 December 2017, several types of information regarding military intelligence were made public, which had been regulated to be kept secret for the sake of Finland's external security", the court said in a release.
The court acquitted an editor whom, it said, did not participate in revealing, among other things, the rough location and tasks of a defence intelligence unit.
The journalists had all denied any wrongdoing.
Prosecutors had sought suspended prison sentences of at least 18 months for the trio.
(Reporting by Anne Kauranen, editing by Terje Solsvik)
