Background: Ayahuasca is a psychoactive Amazonian brew which has emerging data indicating that it has antidepressant and anxiolytic properties. Methods: This paper uses data from the Global Ayahuasca Project (GAP), which was undertaken across 2017–2020 and involved 11912 people, to examine the perceived effects of Ayahuasca consumption on affective symptoms. The study focused on the subsample reporting depression or anxiety diagnoses at time of Ayahuasca consumption. Results: Of participants reporting depression (n = 1571) or anxiety (n = 1125) at the time of consuming Ayahuasca, 78% reported that their depression was either ‘very much’ improved (46%), or ‘completely resolved’ (32%); while 70% of those with anxiety reported that their symptoms were ‘very much’ improved (54%), or ‘completely resolved’ (16%). A range of factors were associated with greater reported affective symptoms improvement, including subjective mystical experience, number of Ayahuasca sessions, and number of personal psychological insights experienced. 2.7% and 4.5% of drinkers with depression or anxiety, respectively, reported worsening of symptoms. Limitations: This study is recognized as a cross-sectional analysis which cannot assess treatment efficacy. Selection bias may exist due to survey-respondents with favorable experience being potentially biased towards participation. Conclusions: Drinkers of Ayahuasca in naturalistic settings perceived remarkable benefits for their affective symptoms in this survey assessment. There is no obvious evidence of negative mental health effects being associated with long-term consumption. Additional randomized controlled trial evidence is required to establish the efficacy of Ayahuasca in affective disorders, and to understand the worsened symptoms reported by a small percentage of drinkers.