The solubility of carbon monoxide (CO) in two isomeric butyraldehydes, n-butyraldehyde and iso-butyraldehyde, which are the products of a hydroformylation reaction in which CO is used as a reactant, was measured by using a variable-volume view cell equilibrium apparatus. The CO solubility was determined by measuring the bubble or cloud point pressures of various CO mole fractions at 10 K intervals from 303.15 to 373.15 K. We found that the solubilities of CO increased with increasing pressures and temperatures and that CO was more soluble in the iso-form (iso-butyraldehyde) than in the n-form (n-butyraldehyde). The measured data was calculated with the PR-EoS incorporated with the conventional van der Waals one-fluid mixing rule. Our measured data showed relatively good agreement with the calculated results with an AAD-p (%) of 2.38% for CO + n-butyraldehyde and 1.57% for the CO + iso-butyraldehyde system.