Background: Cognitive development is one of the most important aspects of child development. Stimulation is essential, especially for children between 1 and 2 years of age. Play materials is one realm where choice is relatively limited. Objective: We investigated the relationships between play materials and cognitive ability. Methods: This large, prospective, community-based cohort study, in the four regions and the capital of Thailand, studied the relationships between toys and cognitive ability in 4,116 children when they reached the first year of life. Details of play toys were collected at home and cognitive scores were measured using the Capute scale two weeks later. Multivariable analysis incorporated the following variables in the final multiple regression model, the 12 types of play materials, study center, parent factors (i.e., age, education, marital status, and income), and child factors (i.e., sex, weight, height, gestational age, birth weight, breastfed, hospital admission, mother-child attachment, number of members in family, number of sibling, iodine consumption, and life events). Results: The first three common materials played with at home included push/pull toys (75.3%), home utensils (75.0%), and sound-making toys (73.9%). Adjusted for the potential factors, five out of the 12 types of play materials were significantly associated with the Capute scale, viz., sound-making toys (p = 0.029), push/pull toys (p = 0.003), creative toys (p = 0.003), natural materials (p = 0.002), and storybooks (p = 0.027). Children who played with natural materials had a higher Capute score than those who did not, with the mean difference of 1.9 (95%CI: 0.7 to 3.1). This was followed by creative materials (mean difference = 1.8, 95%CI: 0.6 to 2.9), and push/ pull toys (mean difference = 1.8, 95%CI: 0.6 to 3.0). Conclusion: The results of the current study underscore the importance that natural materials, creative materials, and push/pull toys be available for children to play with during the first year of life.