Before the procedure, children's pain, anxiety, and fear were assessed by the child, parent, and researcher. In the CBIP group, preparation, briefing, and implementation stages were conducted. The researcher met with the child and parent for preparation and briefing. A volunteer parent was trained to support the child during the procedure (e.g., sitting next to the child, holding hands, talking). Port catheter needle insertion was performed according to unit routine by the same nurse with 5 years' experience, using a single attempt. After the procedure, children rated pain (WB-FPRS), fear (CFS), and anxiety (CAS); the observing parent and researcher also completed CFS and CAS.

In the study, children in the control group will receive the routine clinical procedure prior to the intervention, followed by port catheter needle insertion.

Before the procedure, the researcher initiated social interaction with the child (cognitive distraction). Next, suggestions regarding the procedure were provided (guidance). A volunteer parent sat beside the child, providing support by holding the child's non-procedural hand. While the nurse performed the port catheter insertion, the researcher applied one of the behavioral distraction techniques chosen by the child during the pre-procedure phase, such as counting, singing, reading a poem, or answering questions (behavioral distraction). Upon completion of the procedure, the researcher provided positive reinforcement by praising the child ("Well done!" and "You were very brave!") and rewarding the child with a star and smiley face sticker on the collar (positive reinforcement).

The form was developed by the researchers based on the literature. It consists of 11 questions addressing the sociodemographic characteristics of parents and children, as well as the status of port catheter needle insertion.

Pain will be assessed using the Wong-Baker FACES Pain Rating Scale (WB-FPRS) and completed by the child before and after the port catheter needle insertion. Scores range from 0 to 5, where 0 indicates no pain and 5 indicates unbearable pain.

Fear will be assessed using the Children's Fear Scale (CFS) by the child, parent, and researcher before and after the port catheter needle insertion. Scores range from 0 to 4, where 0 indicates no fear and 4 indicates extreme fear.

Anxiety will be assessed using the Children's Anxiety Scale-State (CAS-S) as reported by the child, parent, and researcher before and after the port catheter needle insertion. Scores range from 0 to 5, where 0 indicates no anxiety and 5 indicates extreme anxiety.