In this paper, we analyze the contracting issues that arise in collaborative services, such as consulting, financial planning, and IT outsourcing. Analyzing first a bilateral relationship, we assume that neither the buyer's nor the vendor's efforts are directly observable, resulting in double moral hazard. We investigate the efficiency of fixed-fee, time-and-materials, and performance-based contracts. We find that fixed-fee contracts are the least responsive to unplanned contingencies, time-and-material contracts are associated with high monitoring costs, and performance-based contracts do not incentivize agents to exert high levels of effort. We then show that our results are robust with respect to the number of vendors involved in the joint production process. On the other hand, the involvement of multiple buyers in the joint-production process creates an additional negative externality, akin to free riding, unless the vendor prescribes all buyers' actions. Our model highlights the trade-offs underlying the choice of contracts in a collaborative service environment and identifies service process design changes that improve contract efficiency.