Brassica is a cool season crop and is susceptible to high temperatures. Developing heat stress tolerant varieties will help the crop to sustain under high temperature and can be used to extend the geographical range of cultivation. We have phenotyped 84 spring type Brassica napus accessions in field under natural heat conditions. Data on various agronomic traits were collected at the end of flowering to maturity stages. An association mapping study was performed to identify QTL associated with heat stress tolerant agronomic traits. A total of 37,269 single nucleotide polymorphism markers were used for this study. Multiple markers distributed on most of the chromosomes were identified. A total of 6, 11, 7, 11 and 7 QTL were identified those explained 52.2%, 71.8%, 53.2%, 73.5% and 61.0% of the total phenotypic variations for plant height, main raceme height, pods on main raceme, pod length, and sterile/aborted pod, respectively. Multiple candidate genes known to be involved in abiotic stress and abortion of different organs were identified in the vicinity of the QTL. For instance, B. napus BnaA03g09160D gene involved in programmed cell death and pollen sterility, BnaA05g33770D and BnaA05g33780D genes associated with pollen sterility and pod abortion were identified in the QTL regions.