The timeliness of audited financial reporting has been a concern for various stakeholders, including shareholders, managers, and regulators, as well as internal and external auditors. In the Kenyan perspective timeliness of audited financial statements is prescribed by the Company Act, 2015 as six months or approximately one hundred and eighty days. The general objective of the study was to evaluate the effect of internal control systems on financial reporting lag among listed companies in the Nairobi Securities Exchange. The specific objectives were; to investigate the effect of corrective controls, preventive controls, detective controls and finally monitoring controls on the on financial reporting lag among listed companies in the Nairobi Securities Exchange. The study was anchored on the following theories; agency theory, stewardship theory, attribution theory and systems theory. The method of study adopted in this study was descriptive research design. The target population of this study l comprised companies listed at NSE. Specifically, the units of analysis will be the four departments of finance, human resources, companies listed at NSE. This study used Purposive stratified sampling method to get the sample size which will sample a suitable number of respondents from the different strata from the NSE companies which operate though board of management. The study used both primary and secondary data to gather information needed to respond to the research objectives. The Panel Data Analysis model was used to determine the significance of each independent variable in affecting the financial performance of companies. Qualitative data as analyzed using content analysis, through developing a thematic framework from the key issues, concepts and themes emanating from the open-ended questions. The study adopted several diagnostic tests that included multicollinearity test, test for fixed or random effects and multicollinearity test. Regarding corrective controls, the study established that corrective controls had a significant and negative effect on the financial reporting lag among listed companies in the Nairobi Securities Exchange. The study also established that preventive controls had a significant and negative effect on the financial reporting lag among listed companies in the Nairobi Securities Exchange. The study further established that detective controls had significant and a negative e effect on the financial reporting lag among listed companies in the Nairobi Securities Exchange. The value of the coefficient is also negative. The study finally established that monitoring controls on had significant and a negative effect on the financial reporting lag among listed companies in the Nairobi Securities Exchange. The value of the coefficient is also negative.