Though magnesium (Mg) alloys are highly attractive for their use as biodegradable/temporary implants, they can be critically compromised in such applications due to their susceptibility to corrosion and stress corrosion cracking (SCC) in human body fluid (such as Hanks’ solution). This study investigated the role of additions of bovine serum albumin (BSA) and glucose to Hanks’ solution in SCC of a Mg alloy, ZK60. The study reproducibly demonstrated the novel and unique characteristic of the acutely elliptical shape of the overall fracture surface of alloy subjected to SCC tests, exclusively when BSA was added to the Hanks’ solution, whereas tests in the Hanks’ solution without BSA produced the fracture surface of usual circular shape. Also, the BSA addition to the Hanks’ solution produced contrasting influences on SCC and electrochemical corrosion. The study provides a comprehensive mechanistic explanation for the two phenomena.