CLN1621, a heat-tolerant tomato cultivars, shows stigma exsertion phenotype at high temperature. The current study deployed the genetic mapping strategy to characterize the genetic components responsible for the stigma exsertion phenotype in the CLN1621 cultivar. The F7 recombinant inbred lines from the cross of CA4 and CLN1621 were used to collect phenotypic data and genotypic data under heat stress and normal growth conditions. The quantitative trait locus (QTL) analysis consistently identified the same stigma exserted QTL in four replicated trials under heat stress growth condition. This QTL is closely linked with the SNP marker 1_3048786 and is located at 32.4 cM on chromosome 1. The effect of this stigma exsertion QTL is attributed to the QTL controlling variation of style length by high temperature.