The process of erection, dismantling and alteration of heights in tower cranes are major safety determinants on construction sites and can result to fatal accidents if the risks involved are not properly managed. Risk factors associated with this process have been identified by some researchers but, no effort was made to scientifically analyse these factors. Hence, the research aimed at assessing safety risk factors during installation and dismantling of tower cranes with a view to establishing the most significant risk factors. A well-structured questionnaire was used to collect data from safety managers, equipment managers and team leaders of installation and dismantling operation with respect to probability/likelihood of occurrence and degree of impact for safety risk factors.Data obtained wereanalysed using descriptive statistics (mean and percentages). From the results, relative significance index score (RSIS) was obtained and evaluated on a 5x5 matrix risk rating scale to determine the criticality of safety risk factors. Results showed that â€•abrasionâ€–had the highest probability of occurrence with a mean value of 3.63 and as such, the most probable factor that occur on site. The study also found that â€•fracture of a wire rope during dismantlingâ€– had the highest degree of impact with a mean value of 4.63 and can result to fatality on site. The latter also had the highest RSIS of 15.6 indicating a high risk factor. This research concludes that fracture of a wire rope during dismantling is a high risk factor and could result from poor maintenance culture that is generally lacking on construction sites