251 Seapuit Road

Osterville, MA 02655


Set on over six acres and accessed via a short causeway, St. Mary’s Island stands as one of Cape Cod’s most unique and idyllic estate properties. The location itself is unmatched, offering complete seclusion in the exclusive seaside community of Osterville, with panoramic views of vaunted North Bay, a sailing and boating epicenter home to Crosby Yacht Yard and Oyster Harbors Marine, and a short distance to The Wianno Club and Oyster Harbors Club. Amidst English gardens and towering beech trees, one finds a majestic French Normandy-style chateau, built in 1920 and carefully updated to exceptional standards. Complete with a deep-water dock and ample carriage house, St. Mary’s Island is a lifestyle property that leaves nothing to be desired.


Main Residence

As one approaches the main residence, stucco and stone walls, steeply pitched gables, and terracotta windows set the stage for the grand scale of the inimitable estate. An arched entry portico opens to the stately entrance hall with oak paneling, soaring ceilings, and ornately carved staircase balusters. The ground floor holds a two-story oak-paneled library with arched casements, lead-paned windows, and a massive fireplace with a staircase leading to a turreted bedroom suite on the mezzanine level. Connected to the library through a secret passage, an intimate study with circular bay windows showcase lovely water views. At the hall’s end, a stunning formal living room boasts floor-to-ceiling windows, a fireplace with a 17th century mantle, and French doors opening to an English stone terrace overlooking manicured grounds and azure water beyond.

A banquet-sized dining room with lofty ceilings and French doors adjoins an immense gourmet kitchen with professional grade appliances that affords entertaining on all scales, while a nearby great room with beamed cathedral ceilings hosts an informal dining area. Additionally, a fully-equipped butler’s pantry, mud room, full bathroom, and powder room, complete the main level, with breathtaking views of North Bay on display throughout.

On the second floor, a large master suite with a luxurious bathroom, walk-in closet, dressing rooms, and kitchenette delivers unmatched privacy and relaxation. Nearby, meandering corridors with well-preserved period details lead to two en suite bedrooms with hardwood floors and fireplace.

Connected to the main house, two discrete guest suites, one with full kitchen, living and family rooms, accommodate guests or staff.  A third guest suite, accessible by private exterior stairs, contains living, sleeping and bath.


Carriage House & Grounds

A stone’s throw from the main residence, a separate carriage house with water views is discreetly tucked into the property’s lush plantings. With full kitchen, living room, bathroom and sleeping areas, this guest house and attached three-car garage augments the refined accommodations available to visitors or staff.

Across the sprawling six acres, the carefully maintained grounds boast manicured lawns, tranquil ponds, English gardens and numerous outdoor living spaces of intimate and grand scale set amongst the rhododendrons and beech trees. Surrounded by water in every direction, this fabled setting delivers an experience of timeless elegance that defies description. Accessed by a stone walkway, the deep-water dock serves as a gateway to Cape Cod’s enviable lifestyle, with endless sailing, fishing, and boating to be enjoyed in one’s backyard.