How does parental causal input relate to children's later comprehension of causal verbs? Causal constructions in verbs differ across languages. Turkish has both lexical and morphological causatives. We asked whether (1) parental causal language input varied for different types of play (guided vs. free play), (2) early parental causal language input predicted children's causal verb understanding. Twenty-nine infants participated at three timepoints. Parents used lexical causatives more than morphological ones for guided-play for both timepoints, but for free-play, the same difference was only found at Time 2. For Time 3, children were tested on a verb comprehension and a vocabulary task. Morphological causative input, but not lexical causative input, during free-play predicted children's causal verb comprehension. For guided-play, the same relation did not hold. Findings suggest a role of specific types of causal input on children's understanding of causal verbs that are received in certain play contexts.