Rounds Mountain is located within Stephentown, New York and Hancock, Massachusetts. It is flanked to the south across the Kinderhook Creek valley by Poppy Mountain and to the southeast by Potter Mountain. The Taconic Ridge continues north from Rounds Mountain as Misery Mountain. The west side of Rounds Mountain drains into East Brook, then Kinderhook Creek, thence into the Hudson River and Long Island Sound. The east side drains into Kinderhook Creek.