As the Internet of Things (IoT) ecosystem expands, accommodating a large number of heterogeneous and resource-constrained devices, there have been concerns about the Quality of Service (QoS) provided by these devices. The IoT ecosystem supports the discovery and integration of services hosted by IoT devices to perform tasks without human intervention. This process allows user-applications to achieve their goal in the dynamic and constantly evolving IoT environment. In such a complex environment, one of the problems is how to resolve QoS contention between IoT service providers and consumer as they spontaneously interact with each other. To address this challenge, this paper presents a dynamic negotiation framework that defines the QoS contract of IoT services based on the current constraints and needs of all the participants in an IoT-aware task. It uses our proposed negotiation model that adapts to the dynamics of the IoT environment. A prototype negotiation framework has been developed and the results illustrate its practicality and the negotiation performance of the adopted negotiation model. © 2019 IEEE.