<p>Spatial skills play an important role in young children’s cognitive development and are strongly linked to later success in mathematics and other academic domains. Construction complexity, which involves developing a range of spatial abilities, can be enhanced through engaging in spatial activities such as LEGO play. Using a multiple-probe design across participants, we examined the effects of a LEGO-based intervention on construction complexity and spatial language use among four children aged 4–5 years in a kindergarten setting. For the intervention, we developed, probed, and taught 15 construction levels. Results showed that children demonstrated greater complexity in their LEGO constructions and used a more diverse range of spatial language. All four participants maintained construction complexity scores above their baseline levels. They also remained highly engaged during the intervention, similar to their engagement during baseline free play. We discuss implications for future research and educational practice, as well as limitations of the study.</p>