The hydroformylation of 10-undecenenitrile (1) – a substrate readily prepared from renewable castor oil – in the presence of rhodium-phosphane catalysts systems is reported. The corresponding linear aldehyde (2) can be prepared in high yields and regioselectivities with a (dicarbonyl)rhodium acetoacetonate-biphephos [Rh(acac)(CO)2-biphephos] catalyst. The hydroformylation process is accompanied by isomerization of 1 into internal isomers of undecenenitrile (1-int); yet, it is shown that the Rh-biphephos catalyst effectively isomerizes back 1-int into 1, eventually allowing high conversions of 1/1-int into 2. Recycling of the catalyst by vacuum distillation under a controlled atmosphere was demonstrated over 4–5 runs, leading to high productivities up to 230,000 mol (2)⋅mol (Rh)−1 and 5,750 mol (2)⋅mol (biphephos)−1. Attempted recycling of the catalyst using a thermomorphic multicomponent solvent (TMS) phase-separation procedure proved ineffective because the final product 2 and the Rh-biphephos catalyst were always found in the same polar phase. Auto-oxidation of the linear aldehyde 2 into the fatty 10-cyano-2-methyldecanoic acid (5) proceeds readily upon exposure to air at room temperature, opening a new effective entry toward polyamide-12.