The study assessed the effects of time and non-time related cost factors on final cost of construction projects in Northern Nigeria. Data on the cost of construction projects were collected directly from projects files of 40 completed building projects in Northern Nigeria using well-designed questionnaires administered to clients, contractors and consultants, selected from the studied states, based on proportionate stratified random sampling technique. WARP6 PLS-SEM software was used in the analysis of the collated data. The results indicated High effects between time and non-time related cost factors and the final cost of building projects in Northern Nigeria. Similarly, linear relationships exist between time and non-time related cost factors and the final cost of building projects. Furthermore, the study provided criteria for assessing the effects of time and non-time related cost factors on the final cost. The study suggests ways of mitigating the effects of these factors (time and non-time related cost factors) on final cost of construction projects in Nigeria, which among others; include adequate estimation, prime cost and provisional sums. Primarily, clients should be cautious of variation orders and comprehensive design before project awards.