The synergistic effect between polyoxometalates (POMs), namely K-5[(SiW11VO40)-O-V]center dot 11H(2)O and H-5[PMo10VV O-2(40)]center dot 13H(2)O and laccase from ascomycete Myceliophthora thermophila has been employed for the first time in oxidative polymerization of catechol. Such a laccase-mediator system allowed the formation of a relatively high molecular weight polycatechol as confirmed by size exclusion chromatography and electrospray ionization mass spectrometry (ESI-MS) (3990 Da when using K-5[(SiW11VO40)-O-V]center dot 11H(2)O and 3600 Da with H-5[PMo10VV O-2(40)]center dot 13H(2)O). The synthesized polymers were applied as dyes for the dyeing of flax fabrics. The color intensity of flax fabrics colored with polymer solutions was evaluated by diffuse reflectance spectrophotometry via k/s measurements (+10% of fixation ratio). A new synthetic process allowed a dyeing polymer, provided upon flax coloration, better color fixation and color resistance when compared to that obtained by conventional synthesis with laccase solely or with addition of organic mediator (1-hydroxybenzotriazole).