Interventions are strongly recommended for preschoolers experiencing participation difficulties in their daily life, regardless of whether or not they have a diagnosis. Best practices recommend that interventions should include the child's significant adults and be delivered in the child's environments. Occupational Performance Coaching (OPC) has shown promising results in improving children's participation by supporting significant adults of school-aged children either with cerebral palsy or without a definite diagnosis, and of preschoolers with developmental coordination disorder. However, this approach has not yet been studied for preschoolers without a definite diagnosis. A multiple case study design was used to explore the interventions's feasibility for this population. Eight parents and three early childhood educators received OPC to help seven children (cases). Intra- and inter-case analyses were conducted to document the effects of the intervention on the children's participation and the caregivers' goals. All children had difficulties in their daily life, and most presented motor, sensory, behavioral and/or adaptive difficulties. Improvements in children's participation and significant adults' satisfaction as well as goal attainment were observed in most cases. Improvements were generally maintained at a three-month follow-up. These findings support the feasibility of OPC for significant adults of preschoolers with participation difficulties in daily life but no definite diagnosis.