Cloud Computing technologies have become the backbone of modern IT infrastructures. Businesses usually adopt a multi-hybrid cloud strategy to achieve optimized portfolios of cloud services provided by different vendors and avoid single vendor lock-in. Meanwhile, this strategy brings technical challenges and complexities to build, manage and operate multi-hybrid clouds. JointCloud is used to refer to but not limited to Hybrid-Cloud, Inter-Cloud, Multi-Cloud, Cloud Federation, Cross-Cloud and Cloud Service Broker (CSB) etc. The IEEE JCC 2021 aims to provide a forum for researchers and practitioners to exchange innovative ideas, latest research results, and practical experiences and lessons learned around JointCloud. The conference will be co-located with IEEE SOSE 2021, IEEE BigDataService 2021, IEEE MobileCloud 2021, IEEE DAPPCON 2021 and IEEE AI TEST 2021. IEEE JCC 2021 will consist of main tracks and special tracks. All accepted papers will be included in the conference proceedings which will be published by the IEEE CPS. Selected papers will be invited for extension and published in selected journals (SCI-Index).