A data integrity solution for mobile agents is presented. The proposed scheme combines digital watermarking and digital signature to achieve the desired security requirements of strong forward integrity, truncation resilience and non-repudiation. The results computed at each hop are first watermarked and then digitally signed. When the agent returns to the home platform we verify the signature first and then extract watermark. Any tampering with the results can be determined in the verification process. We have implemented the proposed scheme with various hashing algorithms like SHA-1, SHA-256 and SHA-512 for a price comparison scenario. For digital signature we have used RSA based signature. We have applied t-test to check the significance of present results. Present experimental results suggest that it can be used in an e-commerce application.