It is left tributary of the Msta and belongs to the drainage basin of the Neva and the Baltic Sea.

It enters Tver Oblast, flows through a number of lakes, and turns north.

It flows through the southeastern part of Lake Piros and turns east.

The drainage basin of the Berezayka includes major parts of Valdaysky and Bologovsky Districts, as well as minor areas at Okulovsky and Borovichsky Districts of Novgorod Oblast and the urban-type settlement of Ozyorny in Tver Oblast.

The towns of Bologoye and Valday lie in the basin of the Berezayka.