Article 176 of the Constitution establishes the County Assembly which shall consist of members elected by the registered voters of the wards; each ward constituting a single member constituency, on the same day as a general election of Members of Parliament, being the second Tuesday in August, in every fifth year;

The number of special seat members necessary to ensure that no more than two-thirds of the membership of the Assembly are of the same gender; the number of members of marginalized groups, including persons with disabilities and the youth, prescribed by an Act of Parliament; and the Speaker, who is an ex-officio member.

The Kajiado County Assembly is the Legislative arm of the County Government responsible for the formulation of laws that regulate the conduct and activities within the County and  provide oversight.

Administratively, Assembly has five directorates which include Office of the Speaker, Office of the Clerk, Legislation, Administration and Finance.

The County has 25 wards across the five sub counties and therefore represented by:

• 25 members who are elected under article 177(a)
• 16 members nominated under article 177(b) of Kenyan Constitution, representing special and marginalized groups.
• The Speaker, an ex-officio member elected in accordance with Article 178 of the Constitution.

The roles of the Assembly as enshrined in the Kenyan Constitution 2010, include; legislation, representation and oversight.  In order to ensure service delivery to the public the top leadership ensures that the electorates come first. This institution has therefore constantly endeavored to ensure that the people of Kajiado County enjoy the best and efficient services.