This study sought to determine the effects of microenterprises support initiatives by the Kiambu County Government on the growth of microenterprises in Thika Sub-County in Kenya. In particular, the study assessed the influence of microenterprises support initiatives concerning policy framework and business skills training by the Kiambu County Government on the growth of microenterprises in Thika Sub-County as well as the moderating effect of firm factors on the relationship between the microenterprises support initiatives by the Kiambu County Government and the growth of microenterprises in the Sub-County. Data was collected using a structured interview schedule from a convenient and randomly selected sample of 100 microenterprises’ proprietors selected from a list of licensed microenterprises operating a wide variety of business categories within the five administrative wards of Thika subcounty namely Township, Hospital, Kamenu, Ngoliba and Gatuanyaga. Analysis of the collected data was by descriptive statistics, simple linear regression and partial correlation. The empirical findings of the study suggest that the overall effect of the microenterprises policy framework support initiatives and business skills training by the Kiambu County Government on microenterprises growth in Thika Sub-County is not statistically significant. The study results also revealed that firm factors namely age of the microenterprise, source of capital, business specialization and educational level of the microenterprises owners have statistically significant inverse moderation effect on the relationship between microenterprises support initiatives by the Kiambu County Government and the microenterprises growth in Thika Sub-County. On the basis of the findings of this study, the Kiambu County Government is urged to first seek to understand aspects of microenterprises support that would have the most impact on the growth of microenterprises in Thika Sub-County by conducting situational analysis and market research undertakings and tailoring support initiatives that are informed by arising insights. For microenterprises support initiatives to be effective, they should take into consideration the underlying contextual factors such as age of the microenterprise and source of capital as well as business specialization and educational level of the microenterprises’ owners. The study findings provide important insights on influence of microenterprises support initiatives and how contextual factors determine the effectiveness of the support initiatives and the ultimate success of microenterprises.