In general, travelers in this part of the world who would like to take their car rentals from Nairobi across the border to Tanzania and Uganda are free to do so; however, there is generally a fee charged by the rental car company to drive your rental car out of the country. You will also need to purchase cross-border insurance from the rental car company; the price for this insurance will vary based on the type of vehicle, the number of days you will have the car across the border, and the number of people that are travelling with you from the car rental location in Nairobi.