The proportion of older adults using medical cannabis is rising. Therefore, we aimed to assess the effects of herbal medical cannabis on the functional status of older adults. We conducted a prospective observational study of patients aged 65 years or older that initiated cannabis treatment for different indications, mostly chronic non-cancer pain, during 2018–2020 in a specialized geriatric clinic. The outcomes assessed were activities of daily living (ADL), instrumental activities of daily living (IADL), pain intensity, geriatric depression scale, chronic medication use, and adverse events at six months. A cohort of 119 patients began cannabis treatment: the mean age was 79.3 ± 8.5 and 74 (62.2%) were female. Of the cohort, 43 (36.1%) experienced adverse effects due to cannabis use and 2 (1.7%) required medical attention. The mean ADL scores before and after treatment were 4.4 ± 1.8 and 4.5 ± 1.8, respectively (p = 0.27), and the mean IADL scores before and after treatment were 4.1 ± 2.6 and 4.7 ± 3, respectively (p = 0.02). We concluded that medical cannabis in older adults has a number of serious adverse events, but was not associated with a decrease in functional status, as illustrated by ADL and IADL scores after six months of continuous treatment.