The way of the mother’s interaction with her child is called maternal interactive style. It has been studied in the context of shared reading. This study aimed to formulate a system of evaluation of the interactive style in shared reading through behavior categories. Categories were constructed from previous studies, and then empirically tested. Fifty-two dyads participated. The average age of the mothers was 35.70 (±6.13) years; the children’s ages varied from 22 to 76 months (Mean = 48.59; Standard Deviation = 17.88). The dyads were filmed in a shared reading interaction. The videos were then analyzed. Agreement analyses (intraclass correlation coefficient) were made between observers in order to test the categories. Most of the categories presented good or excellent agreement, indicating that they were well constructed and properly described. We believe that the system may be useful in future studies investigating the relationship of the maternal interactive style in shared reading with other variables involved.