Gold nanoparticles have been increasingly used in several electronic, material fabrication, and biomedical applications. Several methods have been reported to prepare gold nanoparticles of various shapes and sizes with different photophysical properties. Although useful to prepare gold nanoparticles, most of the methods are not stable enough and undergo degradation, if stored at room temperatures (up to 30 °C) for a few days. In this paper, we report a novel environmentally friendly method to synthesize self-assembled gold nanoparticles in cruciform shapes by using leaf extract of Cannabis indica as a reducing agent without the aid of any polymers or additional chemicals. The nanoparticles are found to be stable for more than a month when stored at room temperature (30 °C). They were able to form stable conjugates with bovine α-lactalbumin protein that may possess anti-cancerous properties.