A 56-year-old male, who is an active intravenous drug abuser (IVDA) (heroin) with a history of diabetes, hypertension, chronic kidney disease, and hepatitis C-related liver cirrhosis, presented with generalized anasarca, bilateral pneumonic infiltrations, and heart failure. His blood cultures were positive for Pseudomonas aeruginosa and were treated with antibiotics. Echocardiogram showed multiple uncommon manifestations of left-sided endocarditis. Surprisingly, he did not have right-sided involvement. Furthermore, echocardiogram revealed undiagnosed large atrial septal defect suggesting a paradoxical seeding of infective vegetation. This case illustrates the uncommon manifestations of Pseudomonas endocarditis in an IVDA and indicates that it is very important to check comprehensively for an atrial septal defect or patent foramen ovale or any shunt in such high-risk patients who may be at risk for left-sided endocarditis which is catastrophic when compared to right-sided endocarditis. If detected early in IVDA patients, these shunts need to be closed to prevent paradoxical embolism of vegetation.