Most cases of cavernosal abscesses result from the progression of sexually transmitted diseases (STDs) commonly caused by Neisseria gonorrhoeae; however, cavernosal abscesses without STDs are rare events. Herein, we describe the first case report of a Lactobacillus paragasseri cavernosal abscess. A 63-year-old man with diabetes and a history of foreign object insertion into the urethra one year prior presented with high-grade fever and slight local pain. The patient was diagnosed with L. paragasseri cavernosal abscess based on computed tomography and microbial biochemical examinations in addition to matrix-assisted laser desorption ionization (MALDI) and 16S rRNA sequencing from blood and pus cultures. The patient was successfully treated with a surgical procedure and appropriate antimicrobials. Hence, L. paragasseri, a commensal bacterium of the gastrointestinal or genitourinary tract, can cause cavernosal abscesses. Notably, L. paragasseri is difficult to distinguish from L. gasseri using MALDI or 16S rRNA sequencing without microbial biochemical examinations owing to morphological similarities. Therefore, special attention should be paid, clinically and microbiologically, to the potential of L. paragasseri cavernosal abscess in clinical settings.