Intra-dot inter-layer magnetostatic coupling have been investigated in trilayers which consist of two [Co/Pt] multilayers with out-of-plane anisotropy and different coercivities separated by a thick Pt layer. For single domain nanodots, the strong intra-dot inter-layer magnetostatic interactions manifest as a shift of the soft layer hysteresis loop. The amplitude of this shift decreases when the size of the dots is increased and/or when the temperature is increased. Satisfactory agreement is found between calculations and experimental results. PACS. 75 Magnetic properties and materials-75.70.-i Magnetic properties of thin films, surfaces, and interfaces-75.60.-d Domain effects, magnetization curves, and hysteresis-75.60.Ch Domain walls and domain structure-75.75.+a Magnetic properties of nanostructures