Purpose: The purpose of this study was to establish the effect of the regulatory environment on the relationship between strategic transport integration and sustainable mobility of Matatu Saccos in Nairobi County, Kenya. Materials and Methods: The study was guided by Positivism philosophy while descriptive research design was adopted. The target population was 177 Sacco Managers and two representatives, one from MOT and other from MVOA respectively. The whole population of 179 respondents was used in the study hence; the study employed the census approach. The questionnaire was pilot tested on 18 respondents who were selected randomly. The study applied Cronbach's alpha and the results displayed a high level of internal consistency hence infers that the research tool used in the study was reliable. The data collection instrument was a semi-structured questionnaire, which were dropped and picked later. A semi-structured interview guide was also used. Data was analysed using descriptive and SPSS Version 24. Results: The findings indicate that there exists a statistically significant, positive effect of strategic integration on sustainable mobility of Matatu Saccos in Nairobi County, Kenya. The R square in the moderated models changed from 71.3% to 80.9% indicating 9.6% increase in variation as a result of the regulatory environment moderating effect. Further, the increase was statistically significant; this implies that regulatory environment does significantly moderate the effect of strategic integration and sustainable mobility of Matatu Saccos in Nairobi County, Kenya. Unique contribution to theory, practice and policy: The study recommended that both the Ministry of Transport and Sacco management develop a punitive measure to curb corruption. The other recommendation is that they should also develop regulatory policies to ensure that vehicles are regularly inspected to confirm their minimum road worthiness to increase safety and increase passenger comfort. This will also promote green environment that will reduce the health hazards of vehicle emission. Additionally, the policy can enhance traffic discipline which is poorly enforced. and also provide basic statistics on transport system.