Research Findings: The focus of the current study was on the frequency and type of number talk of 2.5- and 4-year-old Argentinean children and their mothers (N = 23 dyads) in shared counting-type picture book reading. The book included sets of animals in ascending order (from 1 to 9), with their corresponding numerals and the animals' written names. A finer-grained approach was used for identifying four types of numerical utterances (enumeration, quantification, comparison, and recognition of numerals); for each category, a subset of codes was created to describe how dyads used numerical information for different purposes, intertwining different semiotic modes of communication and reflection with and about numbers. Results showed distinct ways in which mothers and children express and elaborate numerical information, as a function of children's age and set size. Practice or Policy: Shared picture book reading is a simple, low-cost, and effective tool. The results can contribute to the design of books, intervention programs and policies that focus on multimodal contexts for early mathematical development, both in the family and educational environment, with a special emphasis on young children's active participation.