In this study, we developed a one-pot two-step procedure to catalytically convert very high oleic sunflower oil (VHOSO) into hydroxymethylated unsaturated derivatives featuring both primary alcohols and carbon-carbon double bonds. The degree of functionalization in alcohols and C=C double bonds can be accurately controlled affording low and high substituted hydroxymethylated VHOSO. The key point to achieve such control is to partly hydroformylate the C=C bonds at 80 °C and subsequently reduce the reaction temperature to 20 °C to selectively reduced the aldehydes, while keeping a high CO/H 2 pressure. Step growth polymerization of highly substituted hydroxymethylated VHOSO with cyclohexyl isocyanate or 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI) furnish biobased polyurethanes with improved thermal stability compared to similar polyurethanes synthesized from castor oil. Practical applications This study highlights the implementation of triglycerides featuring both C=C double bonds and hydroxymethyl groups. The synthesis proceeds through a one-pot two-steps procedure which consists in a hydroformylation reaction at 80 °C followed by a hydrogenation reaction carried out at room temperature. This simple synthetic procedure is of major interest in a context of an industrial-environmental approach. The high reactivity of the obtained primary alcohols allows the synthesis of bio-PUs displaying untouched C=C double bonds, which could be further functionalized. This finding is of importance as the obtained bio-PUs can be used in many industrial areas such as foams, elastomers, thermoplastics, thermosets, adhesives, coatings, sealants and fibers.