CELF1 and myotonic dystrophy type 1: Here, we show that two heart‐targeting Drosophila DM1 models, Hand > mblRNAi and Hand > Bru3 mimicking sequestration of MBNL1 and stabilization of CELF1, respectively, developed DCM and showed a reduced expression of dmiR‐1 in cardiac cells including cardiomyocytes and pericardial cells.