Nanocomposite scaffolds of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with 1, 2 and 3% (wt) of cellulose nanocrystals (CNC) were produced by thermally induced phase separation. CNC presented an average length of 91 +/- 26 nm and average diameter of 7 +/- 1 nm, determined by atomic force microscopy (AFM). Field emission gun scanning electron microscopy (FEG-SEM) and X-ray microtomography showed porous morphology with interconnected pores, porosity between 41 and 77% and micron-sized CNC dispersion along the samples. Pore distribution after introducing CNC was less regular with an average reduction of 37% in the porosity. The compression modulus was improved about 28% for PHBV/1% CNC, 25% for PHBV/2% CNC and 63% for PHBV/3% CNC. Mouse fibroblasts attached and proliferated better on PHBV/CNC scaffolds surface than on neat PHBV or tissue culture plate controls. After 10 days of cell culture, PHBV/2% CNC sample enhanced cell proliferation with 42%, compared to neat PHBV. Therefore, the addition of CNC can improve both compressive modulus and cell proliferation, making the composite scaffold a potential candidate for tissue engineering.