The audit function has become an integral part of organizational financial management and an instrument of improving performance in the mid- size manufacturing sector (Al-Shammari, 2010). Thus, the internal auditing function gauges the usefulness of manufacturing firms in accomplishing approved purposes and thereby stimulating resilient authority and responsibility in firms. The recommendations made by internal audit for improvement helps management in manufacturing sector entities to improve their risk management, control and governance processes (Van Gansberghe, 2005). The internal audit function offers an unfailing, objective and impartial service to the management, board of directors, and audit committee, while stakeholders are interested in return on investments, sustainable growth, strong leadership, and reliable reporting on the financial performance and business practices of a company (Ljubisavljević & Jovanovi, 2011). Hutchinson and Zain (2009) explored the relationship between internal audit quality (audit experience and accounting qualification) and firm performance (ROE) in Malaysia. The results showed a strong relationship between internal audit quality and firm performance with opportunities of high growth and that this positive link is decreased by the increasing independence of audit committee. Locally, Gaturu and Ngahu (2015) did a study on the effect of computerized audit system on financial management at Water Resources Management Authority in Nairobi County. Their study found that computer-assisted audit techniques and internal controls influenced financial management in WRMA. Their main focus was on computerized audit system and its effect on financial performance of WARMA whose orientation in the sectors of economy is different from that of mid- size manufacturing firms in Kenya. Kiema, Ahmed and Ndirangu (2015) investigated the influence of internal audit independence on the financial performance of small and medium enterprises in the Construction Industry in Mombasa. Kiema et. al., (2015) found that some construction companies within Mombasa County do not accord the internal auditors the independence they deserved to effectively give their opinion on the financial statements of the organizations. The study did not give a clear direction of the relationship between internal audit function as a whole with the financial performance of firms in the mid- size manufactu>