The rapid growth of Internet of Things (IoT)-generated data poses significant challenges in storage efficiency and integrity verification, particularly for resource-constrained devices. Existing cloud deduplication and auditing schemes incur excessive bandwidth and computational overhead, while failing to ensure privacy and delegability in IoT environments. To address these limitations, we propose a privacy-preserving delegable auditing scheme with edge-assisted deduplication, enabling IoT devices to offload computationally intensive tasks such as authenticator generation and audit interactions to fog nodes via securely negotiated delegable keys. Our approach integrates Message-Locked Encryption for data privacy and homomorphic hash-based block tags that simultaneously serve as deduplication identifiers and integrity proofs, eliminating redundant storage and communication. Unlike conventional cloud-based deduplication, our edge deduplication strategy filters out redundant data before upload, significantly reducing bandwidth consumption. To ensure accountability, we leverage blockchain to manage anonymous task delegation and incentive distribution, preventing impersonation attacks. Additionally, a sampling-based verification mechanism empowers devices to validate fog nodes’ honesty by auditing historical logs atomically. Security analysis demonstrates robustness against forgery, while experiments confirm practical efficiency of our proposal.