At Bingham, Teagan Laweryson had 12 of her team-high 14 points in a strong third-quarter effort that saw Valley hold on to edge the Vikings.
The Cavaliers (2-1) expanded a four-point halftime lead to a 14-point margin going into the fourth quarter.
Laweryson also had three rebounds and seven assists to lead Valley, and Kim Bergeron added 11 points and 10 rebounds.
Ashley Hamilton paced Vinalhaven (1-3) with 11 points, and Eliza Davidson had 10.
Vinalhaven 7 10 21 34
Valley 9 14 35 41