The carotenoid biosynthesis pathway of Haematococcus pluvialis has been genetically modified to overproduce astaxanthin, a red pigment of high commercial value. The endogenous phytoene desaturase coding sequence (pds) has been codon optimized and overexpressed in the chloroplast of H. pluvialis under the control of the psbA promoter/UTR. After biolistic transformation and selection, PDS mRNA and protein were detected in transformants. Astaxanthin accumulated up to 67% higher in transformed strains than in wild-type upon induction with high light intensity and nitrogen depletion. This is the first report of plastid transformation of a microalgae with its endogenous pds nuclear gene.