Over 25% of medical marijuana users are cancer patients who use cannabis in conjunction with standard therapy to relieve cancer/treatment-related nausea, anxiety, etc…, 25% of these patients are diagnosed with breast cancer (BC) (half of which are in stage 4 of their disease). World Health Organization declared BC to be the number one cancer worldwide, surpassing lung cancer as of last year. There are certain types of BC that are difficult to treat and often do not have targeted treatments; thus, leading to enhanced disease progression and decreased quality of life. The limited treatment options combined with some BC subtypes exhibiting increased aggressivity has led to BC being the second leading cause of cancer-related deaths in women. Therefore, other treatment options need to be explored, including the use of cannabis as a viable option. In my research, it was first determined that, although low, BC cell lines do express the cannabinoid receptors 1 and 2. Following this, BC cell lines were then treated with varying ratios and combinations of trans-Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). THC and CBD in combination and as a single agent, exhibited anti-neoplastic properties across all BC subtypes, such as anti-proliferative properties and increase in cell death. The most notable combination was the 1THC to 1CBD ratio which has been shown to exhibit the enhanced anti-proliferative effects and cell death in vitro. More specifically, the 1THC to 1CBD ratio is shown to have caused apoptotic properties in vitro. This study provides a starting basis to comprehensively examine the integration of cannabinoids as part of the standard BC treatment regimen, which may be coordinated with use of cannabinoids for symptom relief for BC patients.