The 2010 Constitution of Kenya was expected to enhance service delivery to Kenyans by devolving political and administrative responsibilities to county government. Resources required to support service delivery are from both local revenues and the national government. Observably, local revenue collections have continued dwindling even though empirical studies have not been conducted to analyze this decline. Thus, this study was designed to assess the effect of revenue collection administration and revenue growth in Marsabit County Governments. A descriptive survey design was adopted for this research. The target population consisted of all 209 non-support staff members from the Department of Finance, Economic Planning and Budgeting, and Revenue and Resource Mobilization in the County Government of Marsabit. The respondents in this study were selected using stratified sampling techniques, resulting in 106 respondents. The questionnaires were the primary instrument for data collection, and their validity and reliability were examined through pre-testing of research tools. The secondary data was gathered through existing information from the National Treasury annual reports. Generation of descriptive statistics used SPSS version 26. Inferential statistics was also used to compute correlation analysis as well as multiple linear regression. The findings of the study showed that staff competencies, automation and internal control influenced revenue growth in the County Government of Marsabit. Further, the study established that government policy had a positive moderating effect on the relationship between revenue collection administration and revenue growth in the county government of Marsabit. Inferential statistics results showed a strong R-squared (the coefficient of determination), while the results of analysis of variance (ANOVA) for the regression model showed an F statistic that was within the predictable range. The study concluded that staff competencies, automation and internal control practices strongly influence revenue growth in the county government of Marsabit. The study recommends upscaling of staff competencies by introducing training forums on sensitization of revenue collection administration best practices and investment in digital transactions and improving internal control systems