In a distributed environment like the present Internet, the use of mobile agents for e-transactions cannot be over emphasized. Based on the foregoing, the security of such itinerant codes becomes more critical as the agents criss cross the heterogeneous and seemingly unsafe networks. In this paper, we presented a hybrid scheme comprising of the Caesar Cipher and the traditional Rivest-Shamir Adleman (RSA) algorithm for protecting mobile agents against potentially malicious hosts. This double encryption and double decryption methods can be used to ensure a more secured transaction in an untrusted environment. The empirical results obtained shows that our scheme is computationally more efficient than the traditional RSA in terms of processor overhead and memory/bandwidth utilization.