Over the years, construction firms have often hinged their success on the effective motivation of their employees so as to ensure productivity and improved performance. Previous studies noted that various factors affect the motivational level of employees with regards to work performance. However, due to the difference in employee needs, not all motivational factors have influence on employees’ performance. This study sets out to assess the influence of motivational factors on the performance of employees in construction firms. The study aim was achieved through the identification and assessment of critical motivational factors (intrinsic and extrinsic) in the Nigerian construction firms. Perceptual data was collected from employees of selected construction firms using a structured questionnaire. Data collected was analyzed using descriptive and inferential statistics. Motivational factors were ranked based on respective mean scores from the most to the least influential. Extrinsic motivational factors such as promotion when due, availability of resources and provision of transportation for employees were found to be the most influential factors on performance. Whereas, constant supervision was found to have the least influence on performance. Findings of the study provides construction firms with empirical data on factors that influence the motivation level of employees with a view to optimizing employee productivity. It is recommended that construction firms should pay close attention to the peculiar needs of respective employees which aids in optimizing organizational performance. Keywords: Motivation, Employee performance, construction firms, critical factors