A support structure for an offshore device and a method of assembling and installing the support structure, is provided including a vertical guide sleeve having, three elongated guide sleeves positioned around the vertical guide sleeve, and various braces connecting the elongated sleeves and the vertical guide sleeve. The support structure also includes a transition joint including a cylindrical portion for connection to an offshore device, such as a support tower of a wind turbine assembly, and a convex portion connected to the vertical guide sleeve. The transition joint may include a strengthening material in contact with an inner surface. The vertical sleeve, elongated sleeves, braces, and transition joint can be assembled onshore with lower piles installed in the elongated sleeves, this guide portion of the structure transported to the offshore location, and then piles driven to secure the structure to the floor of a body of water. The support structure minimizes the costs and time associated with material, assembly, and installation, while possessing sufficient strength, and effectively and efficiently handling and transferring loads from the wind turbine to the support surface throughout operation and while maintaining excellent fatigue resisting characteristics to withstand the extensive cyclic loading induced by the wind and waves.