This monograph compares and contrasts the introduction of mathematical proofs in German and Taiwanese mathematics textbooks. The author compared the geometry material of three German and three Taiwanese textbook series for grades 7 to 9 in two general and specialized comparisons. She created an analytical framework to examine textbooks from a quantitative standpoint with regard to the overall comparison. She chose and examined three separate mathematical statements—the Pythagorean theorem, the sum of a triangle’s interior angles, and the Thales theorem—in six textbook series for the specific comparison in order to focus on the differences in how mathematical proofs are introduced in Germany and Taiwan. German and Taiwanese textbooks introduce these three statements in quite different ways. In conclusion, this analysis reveals various geometry content sequences and diverse design priorities for mathematical proofs in German and Taiwanese mathematics textbooks.