In Nairobi County, just like the rest of Kenya, the county assembly is responsible for legislation, oversight, and representation of the county executive who implements the county strategic plans developed from the devolved functions of the devolution. However, the achievement of strategic plans is still with flaws despite this. The purpose of the study was to evaluate the influence of budgeting roles on the implementation of strategic plans in the Nairobi County Assembly in Kenya. The study was guided by the McKinsey 7s model, the Dynamic Capability Model, and the Resource-Based View Theory. The study was conducted using a quantitative research design. The target population was 123 members of the County Assembly, consisting of 85 elected and 38 nominated members. The population also included 3 officials from the County Assembly's Financial and Budget Office, Procurement Office, and Planning Department. The study involved 85 elected and 38 nominated county assembly members, using simple random sampling. Officials from the Financial and Budget Office, Procurement Office, and Planning Department were selected by census. Primary data was collected with 5-point Likert scales. SPSS regression analysis tested the relationships between dependent and independent variables, with multiple regression used due to activity interconnectedness. Results were presented in descriptive figures and tables, with regression outcomes shown in tables. The study's findings indicate that MCAs perceive their budgeting responsibilities favorably, and a positive correlation, (r = 0.833, p < 0.01) is found between their budgeting roles and strategic plan implementation. Following these findings, the study recommends the need to enhance Nairobi City County Government (NCCG)'s budgeting by training MCAs in advanced techniques and enabling them to oversee budget utilization in line with priorities. MCAs should continuously build capacity to understand compliance, ethics, risks, and plan adherence, promoting collaborative oversight.