Investment and upkeep shutdowns will weaken second-quarter results by nearly 14m, said the firm, while the strikes had wiped out almost 3m.
The quarter will also include 3.4m of costs from job cuts in Germany and Austria, a spokesman said.
The Stockstadt mill in Germany is to lose 140 staff by 2008, while Austrias Hallein mill will lose 100. M-real hopes to make annual savings of around 10m.
"Weakened results in Finland were caused by the two-week shutdown at the Simpele mill," said president Hannu Anttila (pictured). The mill has also undergone 41m worth of capacity upgrades.
Frances Alizay paper and pulp mill shut for nearly three weeks for around 6m of improvements.
Meanwhile, around 20,000 Finnish paper workers downed tools last month in a two-day wildcat strike over job cuts.
In M-reals first-quarter results, a pre-tax loss of 7.5m last year had jumped to an 11m profit in 2006. Anttila said second quarter results were expected to be weaker than the first.
M-real profit hit in second quarter
M-real has taken a 17m (24m) hit after racking up huge costs from kit upgrades and the recent Finnish paper mill strikes.