Your baby may be able to stack one block or small object on top of another by 10 to 12 months of age. By around 16 to 18 months, your toddler may be able to stack two or three blocks, progressing to a “tower” of four to six blocks by around 18 to 24 months. Your child’s stacking ability will continue to progress throughout the toddler and preschool years, supporting both motor skills and creative play.