Objectives: This paper explores the relationship between speech therapy intensity and parent satisfaction with speech therapy (ST) in children with Phelan-McDermid Syndrome (P-MS), a rare genetic disorder. Methods: ST intensity ("ST Dose [minutes per session]") × ("ST Dose Frequency") × ("ST Length [years]") and parent satisfaction (modified PSQ-18) with ST were measured by online questionnaire. Non-parametric correlation, partial correlation, and linear regression calculations were performed. Results: Significant correlations between ST Dose and parent satisfaction were observed in the subscales of Time Spent with ST (r = 0.36, p < 0.05) and Accessibility and Convenience (r = 0.40, p < 0.05) in children with P-MS controlling for child age. ST Dose was also a significant independent predictor of parent satisfaction with ST in specific subscales. Conclusion: Significant positive correlation and linear regression results indicate increases in ST Dose (minutes per session) represent a mechanism for increasing parent satisfaction with ST in children with P-MS.