This two-volume set LNICST 680-681 constitutes the refereed proceedings of the 21st EAI International Conference on Collaborative Computing: Networking, Applications and Worksharing, CollaborateCom 2025, held in Shanghai, China, during November 15–16, 2025.The 58 full papers included in these volumes were carefully reviewed and selected from 207 submissions. They are categorized under the topical sections as follows:  Part I: Large Language Models & Recommendation systems; and Deep Learning and application.Part II: Federated Learning & Collaborative working; Edge computing & Task scheduling; Security and Blockchain applications; and Anomaly Detection.

This two-volume set LNICST 680-681 constitutes the refereed proceedings of the 21st EAI International Conference on Collaborative Computing: Networking, Applications and Worksharing, CollaborateCom 2025, held in Shanghai, China, during November 15–16, 2025.The 58 full papers included in these volumes were carefully reviewed and selected from 207 submissions. They are categorized under the topical sections as follows:  Part I: Large Language Models & Recommendation systems; and Deep Learning and application.Part II: Federated Learning & Collaborative working; Edge computing & Task scheduling; Security and Blockchain applications; and Anomaly Detection.