Two rice doubled haploid (DH) populations derived from the crosses of ZYQ8/JX17 and CJ06/TN1 were used to detect quantitative trait loci (QTLs) for flag leaf length (FLL), width (FLW), and angle (FLA) under long-day conditions in Hangzhou (subtropical zone) and short-day conditions in Hainan (tropical zone), China. The four parents differed significantly in all 3 traits. FLL was found to be positively correlated with FLW in the 2 populations. A total of 30 QTLs were identified for flag leaf traits, with a contribution to the phenotypic variation of each QTL from 4.49 to 26.30%. Among these, qFLL-4b, qFLW-12, and qFLA-2a showed larger additive effects on the phenotype and explained more variations compared to the other QTLs. qFLL-1a and qFLL-8 were detected in both environments, while qFLL-2, qFLL-3, qFLL-10, qFLL-12, qFLW11, qFLW2, and qFLA8 were novel QTLs, which may be beneficial to rice ideal-type breeding.