Following legalization, Medical Marijuana (MM), has been used to treat the symptoms of Amyotrophic Lateral Sclerosis (ALS), yet data regarding Medical Marijuana's efficacy is lacking. Thus, we conducted a retrospective cohort study to assess Medical Marijuana's impact on ALS symptoms and progression. We reviewed the charts of all ALS patients treated in our clinic over a two-year period to collect data related to the primary outcome measures of symptoms of pain, poor appetite, anxiety, spasticity, insomnia, ALSFRS-R score, BMI, and MM use. Two groups were defined: a control group with target symptoms but no MM prescription, and a test group that filled a MM prescription, including a subgroup on MM for ≥3 visits. Outcomes were correlations between MM usage and symptom prevalence, and between MM usage and BMI and ALSFRS-R decline slope, analyzed using descriptive statistics and qualitative analysis via local regression. Data included 344 ALS patients. We found MM use correlated with alleviation of pain, poor appetite, and anxiety in the short term, but not with spasticity or insomnia. There was no correlation between MM use BMI maintenance. Notably, MM usage correlated with faster ALS progression, although patients using MM exhibited higher symptom burden and progressed faster than controls even pre-MM prescription. In conclusion, MM shows correlation with managing pain, poor appetite, and short-term anxiety in ALS, but is also correlated with faster disease progression based on ALSFRS-R scores. We suggest a multi-center, randomized controlled trial to evaluate both the clinical efficacy and safety of MM in the treatment of ALS.