The redox behavior of a synthetic hemoprotein, the recombinant human serum albumin (rHSA), incorporating a tetraphenylporphinatoiron derivative (FeP) [rHSA-FeP] was first evaluated using a graphite electrode modified with didodecyldimethylammonium bromide as a promoter. Compared to that of the naked FeP, the redox potential of the Fe(III)/Fe(II) couple in rHSA-FeP shifts in the positive direction, indicating that the central ferrous ion of FeP becomes more difficult to be oxidized by incorporation into the albumin structure.