The OVATE family proteins (OFPs) are plant-specific proteins that modulate diverse aspects of plant growth and development.  In tomato, OFP20 has been shown to interact with TONNEAU1 Recruiting Motif (TRM) proteins to regulate fruit shape.  In this study, we demonstrated that the mutation of StOFP20 caused a shift from round to oval shaped tubers in a diploid accession C151, supporting the role of StOFP20 in controlling tuber shape.  Its expression reached a maximum in the tuber initiation stage and then decreased as the tuber develops.  To help elucidate the mechanism of tuber shape regulation by StOFP20, 27 TONNEAU1 Recruiting Motif (TRM) proteins were identified and 23 of them were successfully amplified in C151.  A yeast two-hybrid assay identified three TRM proteins that interacted with StOFP20, which was confirmed by firefly luciferase complementation in tobacco leaves.  The OVATE domain was indispensable for the interactions, while the necessity of the M10 motif in TRM proteins varied among the interactions between StOFP20 and the three TRMs.  In summary, both StOFP20 and SlOFP20 directed interactions with TRM proteins, but the corresponding interactants were not completely consistent, implying that they exert regulatory roles through mechanisms that are only partially overlapping.