Disease resistance improvement remains a major focus in breeding programs as diseases continue to devastate Brassica production systems due to intensive cultivation and climate change. Genomics has paved the way to understand the complex genomes of Brassicas, which has been pivotal in the dissection of the genetic underpinnings of agronomic traits driving the development of superior cultivars. The new era of genomics-assisted disease resistance breeding has been marked by the development of high-quality genome references, accelerating the identification of disease resistance genes controlling both qualitative (major) gene and quantitative resistance. This facilitates the development of molecular markers for marker assisted selection and enables genome editing approaches for targeted gene manipulation to enhance the genetic value of disease resistance traits. This review summarizes the key advances in the development of genomic resources for Brassica species, focusing on improved genome references, based on long-read sequencing technologies and pangenome assemblies. This is further supported by the advances in pathogen genomics, which have resulted in the discovery of pathogenicity factors, complementing the mining of disease resistance genes in the host. Recognizing the co-evolutionary arms race between the host and pathogen, it is critical to identify novel resistance genes using crop wild relatives and synthetic cultivars or through genetic manipulation via genome-editing to sustain the development of superior cultivars. Integrating these key advances with new breeding techniques and improved phenotyping using advanced data analysis platforms will make disease resistance improvement in Brassica species more efficient and responsive to current and future demands.