Artificial enzyme activators are of great interest for enzyme applications in a wide range of research fields. Here, we report an enzyme hyperactivation system using polyelectrolytes that are complementary to charged substrates. The enzyme activity of α-chymotrypsin (ChT) for a cationic substrate increased 7-fold at pH 7.0 in the presence of anionic poly(acrylic acid) (PAAc) and for an anionic substrate increased 18-fold at pH 7.0 in the presence of cationic poly(allylamine) (PAA). Analysis of salt and pH effects, enzyme kinetics, dynamic light scattering (DLS), and circular dichroism (CD) indicated that the enzyme activation results from favorable electrostatic interactions between oppositely charged substrates and polyelectrolytes surrounding the enzymes. This hyperactivation system does not require laborious mutagenesis or chemical modification of enzymes and thus is relevant to a number of applications.