Knowledge of the fidelity with which interventions are delivered in research studies is crucial to meaningful examination of intervention impact. This paper presents a review of fidelity implementation (FOI) measurements in interventions jointly delivered by speech-language pathologists (SLP) and parents in research for preschool-aged children who stutter (CWS). Four key FOI components were examined: dosage, adherence, quality, responsiveness. Thirty-six studies met the inclusion criteria for this study. Articles were published between 1990 and 2020 described nine different interventions and examined CWS aged 2–6 years. No study reported all FOI components in both the clinical and the home setting and five did not report on any FOI component in either setting. The number of FOI components reported ranged from 0 to 4 in both clinical (M = 1.5) and home (M = 1.0) settings. Across studies, dosage was most often reported (n = 27, 75.0%) and responsiveness was least often reported (n = 16, 44.4%). The number of FOI components reported in articles did not increase over time, although a trend towards greater reporting in recent years was observed. Poor reporting of FOI in intervention research presents a serious methodological concern that impacts the ability of clinicians and researchers to interpret the findings of these studies. Rigorous measurement and reporting of FOI in future intervention studies is required in order to better inform evidence-based practices for interventions with CWS.