Abstract
Given a quasi-modular form f of nonzero weight for SL 2 (ℤ) with algebraic Fourier coefficients, we consider the nonzero values of f at the algebraic points of the moduli space SL 2 (ℤ)ℍ. We show that these special values are transcendental numbers. We also establish the analogous result in the setting of Drinfeld quasi-modular forms. © 2012 by Walter de Gruyter Berlin Boston.