Toys help children in mastering developmental tasks. This study investigated toy effect on children with developmental disabilities as they engage in using ordinary and adaptive toys. A single-subject design was used to identify the effects on their toy play abilities. Differences in toy effects between playing ordinary and adaptive toys were examined. Three special education teachers chose ordinary toys and modified ordinary toys. Modified ordinary toys, i.e., adaptive toys, were designed according to the individual disabilities of participating children, treatment goals, and the toy types. Three children with developmental disabilities from pre-schools in Taiwan were enrolled. Appropriate participation of three pre-schoolers increased dramatically in playing adaptive toys during intervention phase. The toy effects demonstrate that when using adaptive toys, children with developmental disabilities may response better during toy play sessions. (Contains 2 tables.)