Commercially available cellulose acetate butyrate (CAB, unplasticized) was blended in melt and solution with lignin esters having different ester substituents-acetate (LA), butyrate (LB), hexanoate (LH), and laurate (LL). All lignin esters formed phase-separated blends with CAB with domain size depending on processing conditions and the interaction between phases depending on blend components. CAB/LA and CAB/LB revealed the strongest interactions with domain sizes on the 15-30 nm scale as probed by dynamic mechanical thermal analysis and differential scanning calorimetry. The glass transitions (T-g,) followed the Fox equation. Broader transitions corresponding to the T-g,s of the two parent components were observed for CAB blends with LH and LL. Transmission electron micrographs revealed differences in the phase dimensions of the blends in accordance with chemical and processing (i.e., melt vs solvent) differences. Modest gains in modulus were observed for low contents (<20 wt %) of LA and LB.