We consider a boundary version of the Schwarz Lemma on a certain class of functions which is denoted by . For the function f(z) = z + a₂z² + a₃z³ + … which is defined in the unit disc D such that the function f(z) belongs to the class , we estimate from below the modulus of the angular derivative of the function f″(z)f(z) at the boundary point c with f′(c) = 0. The sharpness of these inequalities is also proved.

Keywords: holomorphic function, the Schwarz lemma on the boundary, Jack's lemma, angular derivative.