Mycobacterium tuberculosis infection is endemic in Taiwan, and an acid-fast bacilli (AFB) smear-positive specimen is a diagnostic reference for mycobacterium infection. Systemic mycobacterium infection or mycobacteremia will be suspected first if an AFB-positive blood smear is documented. Here, we report the case of a patient who had concomitant Mycobacterium avium complex and Nocardia nova bacteremia presenting with AFB-positive blood smears, and emphasize the importance of the differential diagnosis of a positive acid-fast stain.