Research Findings: Shared-picture book reading can stimulate children's mathematical development. Evidence of learning-supportive characteristics in picture books is limited in this domain. A first step is systematically analyzing the occurrence of domain-specific features in publicly available picture books. We analyzed the occurrence of general book features, features of numbers and quantitative language, and features of sets in 100 mathematical and 45 matched non-mathematical picture books written in Dutch. The results indicated variety among picture books, but more than 50% of the mathematical picture books focused on the 1-10 number range and ascending counting, and less than 20% paid attention to the counting principles and other numeracy skills. Quantitative language was included in 75% of the mathematical picture books, but infrequently across pages and with little variety in wording. Mathematical picture books with a story hardly differed from picture books without a story regarding the presence of domain-specific features. Finally, fewer non-mathematical picture books included mathematical content and generally on less pages compared to mathematical picture books. Practice or Policy: These findings stress the importance for picture book developers and teachers and parents to, respectively, design and select picture books in view of literature regarding children's mathematical development.