Chronic lymphocytic leukemia (CLL) is characterized by immune dysfunction and increased susceptibility to bacterial infections. Growing antimicrobial resistance has renewed interest in bacteriophage therapy (PT) as a complementary antimicrobial approach. However, naturally occurring anti-phage antibodies may affect its efficacy. This study investigated the upper respiratory tract microbiota of newly diagnosed, untreated CLL patients with no prior exposure to therapeutic phages. A total of 51 bacterial isolates were recovered from 22 CLL patients and 14 isolates from 12 healthy volunteers. Staphylococcus aureus was the predominant species, followed by coagulase-negative staphylococci (CoNS). Antimicrobial susceptibility testing revealed the highest susceptibility (82.35%) to linezolid and moxifloxacin, whereas several S. aureus isolates showed reduced susceptibility to glycopeptides. Commercial phage preparations showed weak or no lytic activity against most isolates, particularly CoNS. In contrast, all 12 S. aureus isolates from CLL patients and healthy volunteers were susceptible to phage PSA-1 from the Pyophage preparation, with an efficiency of plating (EOP) of 0.7-1.0. Naturally occurring anti-phage antibodies were detected in both groups. The mean phage neutralization constant (K) was 0.64 ± 0.12 in CLL patients and 0.28 ± 0.06 in healthy controls, indicating variable pre-existing humoral immunity that may influence phage activity. These findings indicate that upper respiratory isolates from untreated CLL patients remain largely susceptible to conventional antibiotics. Phage therapy may represent a promising adjunctive strategy for managing S. aureus infections in CLL patients. Assessment of phage susceptibility and anti-phage antibody levels may optimize future phage-based therapies.