The purpose of the research was to evaluate the effectiveness of the Safe and Sound ProtocolTM (SSP) on sensory sensitivities, digestive problems, and selective eating in individuals with autism spectrum disorder, hypothesizing a progressive decrease in symptoms at the 1-week and 4-week follow-up assessments that may be moderated by age. The effectiveness of SSP was evaluated in a prospective single-arm study, using validated caregiver reports and self-reports. Thirty-seven participants with ASD (aged 7 to 39 years) took part in the study. Auditory hypersensitivities, auditory hypo-sensitivities to voices, visual sensitivity, and digestive problems all declined at the 1-week and 4-week follow-up assessments. Tactile hypersensitivities and selective eating declined at the 4-week follow-up assessment. At the 4-week follow-up assessment, 70.3% participants showed ≥30% change in at least one domain (Cohen’s d range, week-4: .22 to .50). Age moderated some effects, as adolescents showed a reduction in visual hypersensitivities and non-social tactile sensitivity. Adult participants had a decrease in tactile sensitivities at the 4-week follow-up assessment. Results support use of SSP as a promising intervention to reduce sensory sensitivities, digestive problems, and selective eating in individuals with ASD and highlight the need for controlled clinical trials in natural settings, with considerations for control conditions and testing mechanisms of effects.