Background: This study investigated the effects of forest play activities on toddlers' attention span and environmental sensitivity. The subjects of the study were 4-year-old toddlers in two classes at T Children's Center in S City, randomly assigned to experimental and comparison groups. The data collected were analyzed using SPSS. Materials and Methods: In this prospective randomized controlled study, the t-test and ANCOVA were conducted using the 26.0 program. The results showed that, first, the attention span of toddlers in the experimental group who practiced forest play activities was statistically significantly higher than that of the comparison group, and second, the environmental sensitivity of toddlers in the experimental group who practiced forest play activities was statistically significantly higher than that of the comparison group. Results: The study demonstrated that the forest play activities had a statistically significant effect on both attention span and environmental sensitivity in toddlers from the experimental group compared to the comparison group. Conclusion: This study provides empirical evidence of the positive effects of forest play activities on toddlers' attention and environmental sensitivity, suggesting that early childhood education professionals should implement forest play activities more systematically and consistently.