Public Commissions in Kenya are importance arms of the executive in the management of constitutional affairs. The aim of this study was to investigate the effects of internal audit on performance of public commissions in Kenya. The specific objectives of the study were; to determine the effect of expertise of the internal auditing staff on the performance of Public Commission in Kenya, to examine the effect of internal audit controls on the performance of Public Commissions in Kenya and lastly, to investigate the effect of top management support of internal Audit on performance of publicCommission in Kenya. Parliamentary service commission was the proxy for public service commissions in Kenya. The study was underpinned on two theories namely the agency theory and institutional theory. The study targeted members of internal audit committee of the twelfth parliament – (first session) the national assembly membership of committees. These are the public accountants (19 members), public investment (19 members) and the special fund accounts committee (19 members). Thus, the target population of the study will be 57 people. Due to the population size of parliamentary commission, the study took the census approach to collect data from all the members of the audit committee in the parliamentary service commission. The study followed adescriptive study design. Primary data was collected by the use of questionnaires.