There's different information on this one.
According to Serebii, yes:
>Status moves shall still go through and various other moves such as Feint and Phantom Force will break it (Mat Block).
Source - Serebii
However, according to a Smogon test, no:
>Conclusion: Feint does not lift the effect of Mat Block. Naturally, because it hits before you use Mat Block. Phantom Force and thus Shadow Force DO lift the effect of Mat Block, but likely only if it hits after Greninja uses it.
The Smogon one makes much more sense, as Mat Block isn't like Protect, which has increased priority, therefore Feint should fail because it's +2 while Mat Block is +0, meaning Feint would fail because Mat Block isn't even up yet when Feint is used.
So I would say that Serebii made a mistake, and Smogon is correct in saying that Feint does not negate Mat Block.
Source - Smogon