Play is an essential component of a healthy childhood, often manifesting even in difficult ecological settings. The instrumental nature of play and its role in development has been the focus of research for a long time, especially in the case of children with special needs. Existing literature presents contradictory opinion on how play of preschool children with Intellectual Disability (ID) differs from their typical peers, based on comparison of their play skills and complexity. There is also a gap in existing knowledge on designing for play of these children, with lack of theoretical frameworks and guidelines for design practitioners. The main objective of the present thesis is to study the relationship between design characteristics of play artefacts/activities and observed playfulness of preschool children with mild to moderate ID. Playfulness has been used as a handle to account for the experiential and affective components of play activity and an assessment framework has been developed over the course of the thesis, based on Sanderson’s (2010) construct. The thesis follows a sequential, exploratory mixed-methods design, where play interactions of children with a variety of age-appropriate toys are analyzed in a free play context using a qualitative analytical framework derived from Classical grounded theory (Glaser, 1998). With the perspective of a design activist, a number of useful actionable insights have also been reported for design practitioners and facilitators. A playfulness assessment framework has been developed which could be used to compare individual play episodes and observe the effect of interventions. Lastly, an initial proposal is made for a model useful for design practitioners to control the features in toy design using the dimensions and aid in the idea generation process for developing playful solutions, which would need further validation.