With only three sources of resistance currently known to race 6 of Pseudomonas syringae pv. phaseolicola (Burkholder) (Psp) which causes halo blight, an important bacterial disease of common bean, there is an urgent need to identify additional sources of resistance. Therefore, 283 accessions of common bean from the USDA-NPGS core collection were evaluated for resistance to race 6 of Psp under greenhouse conditions. Using unifoliate leaf inoculation method, a total of 13% of accessions were resistant. Five of these accessions, PI 201329, PI 309810, PI 310826, PI 319592, and PI 533259, displayed the highest levels of resistance with mean halo blight score of 1.1. Unifoliate vs trifoliate inoculation methods were also evaluated. Significantly higher mean (4.0) and range (1.0-7.0) of halo blight severity was observed at trifoliate stage compared to unifoliate stage, 2.0 and 1.0-2.4, respectively. A significant positive but weak correlation (r2=0.17) of halo blight severity between trifoliate and pod inoculation methods within an individual plant suggests that disease resistance may be controlled by independent genes prevalent at each plant developmental stage. Halo blight severity observed in trifoliate leaves and pods under greenhouse condition was later validated under field condition. Significantly higher mean disease score and range of 4.7 and 2.3-7.1 were reported at pod stage compared to 3.6 and 2.0-6.6, respectively, at trifoliate stage. However, PI 313217 showed consistent resistant reaction across all plant development stages, i.e., unifoliate, trifoliate, and pod, under both field and greenhouse conditions. A significant but weak correlation (r2=0.21) between halo blight severity in trifoliate leaves and pods under field condition confirmed the greenhouse results. To identify genomic regions associated with resistance to race 6 of Psp, genome-wide association mapping study (GWAS) was employed using 197 accessions and 4707 single nucleotide polymorphism (SNP) markers. Three significant regions were identified, of which two novel regions in Pv04 and one in Pv05 controlled for 19% of the phenotypic variation. The significant SNPs could be used in marker assisted selection (MAS) for the improvement of common bean breeding program with focus on resistance to race 6 of Psp.