Herein, we report results on olefin self-metathesis in the presence of low catalyst loadings as an efficient approach for the synthesis of α,ω-difunctional monomers from plant oils containing a high ratio of polyunsaturated fatty acids. It was clearly observed that the driving force for the synthesis of the C18-diester was the formation of cyclohexa-1,4-diene and hex-3-ene, both of which, in contrast to self-metathesis of oleic acid methyl ester, can easily be removed from the reaction mixture by distillation and thus help to shift the metathesis equilibrium to full conversion. The resulting unsaturated C18-diester was hydrogenated and subsequently converted to the corresponding diol. Both monomers were used for the synthesis of a long-chain polyester in the presence of 1,5,7-triazobicyclodecane (TBD) as a catalyst. The molecular weight of the resulting polymer was determined by static light scattering. Moreover, DSC analysis was applied to determine the thermal properties of the final polymer.