Randomized studies have reported a positive effect of candesartan, an angiotensin II receptor antagonist, in migraine prevention. The aim of our study was to explore patient subjective efficacy of candesartan in a real-world sample of migraine patients and try to identify predictors of candesartan response. We audited the clinical records of 253 patients who attended the King’s College Hospital, London, from February 2015 to December 2017, looking specifically at their response to candesartan. Univariate and multivariate logistic regression models were used to identify predictors of headache benefit. Odds ratios (OR) with confidence intervals (CI) 95% were calculated. Eighty-one patients (chronic migraine, n = 68) were included in the final analysis. Thirty-eight patients reported a positive response to candesartan, while 43 patients did not have a meaningful therapeutic effect. The median dose of candesartan was 8 mg and the median treatment period was 6 months. In a univariate logistic regression model, the presence of daily headache was associated with reduced odds of headache benefit (OR 0.39, 95% CI 0.16-0.96, p = 0.04). In multivariate logistic regression model, younger age (OR 0.92, 95% CI 0.87-0.98, p = 0.006) and longer disease duration (OR 1.06, 95% CI 1.01-1.12, p = 0.03) were associated with a good response to candesartan, while the presence of daily headache was associated with reduced odds of headache benefit (OR 0.16, 95% CI 0.04-0.71, p = 0.01). Having failed up to nine preventives in patients did not predict a treatment failure with candesartan as well. Candesartan yields clinical benefits in difficult-to-treat migraine patients, irrespective of previous failed preventives.