Primary cardiac diffuse large B cell lymphoma (PC-DLBCL) is a rare kind of hematological malignancy, and its clinical and pathologic characteristics, especially in Eastern countries, remain unclear. Moreover, genomic alterations in PC-DLBCL have not been studied previously. We describe a case of a 57-year-old man who presented with exertional dyspnoea due to a heart mass in April 2018 and was diagnosed with PC-DLBCL characterized by immunohistochemical markers of the activated B cell (ABC) subtype and double expression of c-MYC and Bcl-2. Mutations in a total of 11 genes-TBL1XR1, CD79B, IGLL5, ZMYM3, MYD88, TMSB4X, PIM1, BTK, NRXN3, CUX1, and CSMD1-were detected via next-generation sequencing (NGS), while 19 copy number variations (CNVs) such as 1q+, 3p+, 3q+(*2), 5p+, 6p-, 6q-, 7q+, +11, 12q-, 15q-, 17q+, 17p-, +18, 19q+, 19p-, 19q-, X q+, and -Y and 4 copy-neutral loss of heterozygosity (CN-LOH) lesions located at 1q21.1q44, 3p26.3q11.2, 3q13.11q29 and 6p22.2p21.32 were identified by single nucleotide polymorphism (SNP) array karyotyping. Some key gene alterations in lymphoma, such as PRDM1 deletion and Bcl-2 amplification, were identified using SNP array analysis. The patient received 6 courses of chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone, R-CHOP regimen) after surgery and is currently in remission. In summary, the present case was diagnosed as PC-DLBCL, ABC subtype by the Hans algorithm and double expression lymphoma, with co-occurrence of the MYD88L265P and CD79B mutations (MCD) subtype by genetic alteration analysis. This study presents a unique PC-DLBCL case in which complex genomic alterations were revealed by NGS and SNP array analysis, which has never been reported in the literature, and these findings could provide new insight into the genomic characterization of PC-DLBCL.