Forty private companies involved in solid waste collection (SWC) in five Ethiopian cities were studied to identify key factors affecting their service performance. Investments, operational management capability and regulation are the factors investigated. The major determinants of SWC according to a regression analysis are number and carrying capacity of vehicles, distance from disposal sites and (unobserved) city characteristics. Route planning and a more flexible contract substantially increase collection. Investments in SWC depend on access to capital by the private companies. Different experiences of regulation (scope of contract) on SWC have been noticed. Service contract arrangements are impediments in Mekelle. While, service zoning allows competition in Addis Ababa, Hawasa and Bahir Dar. Rectifying the challenging nature of the contracts for private sector involvement (PSI) in SWC is vital so that the cities with large heaps of solid waste left uncollected become clean. The study findings suggest that for a number of reasons the Ethiopian government needs to entrust private companies with opportunities for more meaningful and sustainable involvement in SWC. We recommend that the contract shall also have conditions concerning sustainability.