INTRODUCTION: On 1 May 2018 Scotland introduced a minimum unit price (MUP) of GB50 pence per unit of alcohol (8 g) sold. We analysed household purchase data to assess the impact of MUP in shifting purchases from higher to lower strength beers. METHODS: Data from Kantar Worldpanel's household shopping panel, with 75 376 households and 4.76 million alcohol purchases, 2015-2020. We undertook interrupted time series analyses of the impact of introducing MUP in Scotland on changes in the proportion of the volume of purchased beer with an alcohol by volume (ABV) ≤3.5% using purchases in England as control. We analysed the moderating impact of the volume of purchased beer with an ABV ≤3.5% on the size of the associated impact of MUP in reducing purchases of grams of alcohol within beer. RESULTS: MUP was associated with a relative increase in the proportion of the volume of beer purchased with an ABV ≤3.5%, Scotland minus England, of 10.9% (95% CI 10.6-11.1), following a 43.6% (95% CI 40.1-47.1) increase in the volume of beer purchased with an ABV ≤3.5%, and a 9.6% (95% CI 9.4-9.8) decrease in the volume of beer purchased with an ABV >3.5%. MUP was associated with reduced purchases of grams of alcohol within beer by 8% (95% CI 7.8-8.3), increasing to 9.6% (95% CI 9.3-9.9), when accounting for the moderating impact of shifts to lower strength beer. DISCUSSION AND CONCLUSIONS: MUP seems an effective policy to reduce off-trade purchases of alcohol and encourage shifts to lower strength beers.