The number of prosthetic joint infection (PJI) cases is increasing along with total joint arthroplasties. There is currently no diagnostic test available with 100% sensitivity to identify PJI. The aim of the study was to assess and compare two different bacteriophage K-based methods with standard microbiological culturing methods to detect staphylococci. Samples were retrieved from 104 patients undergoing revision surgery due to suspected PJI. Implants were subjected to sonication and sonicate fluid (SF) was assessed with the methods of qPCR detection of bacteriophage K DNA and adenosine triphosphate (ATP) detection after bacteriophage K lysis. The results were compared with the results of standard microbiological culturing methods. PJI was confirmed in 33 cases according to the PJI definition. Using the methods of ATP and bacteriophage K DNA detection 100% specificity and predictive value were achieved. The sensitivity of qPCR detection was higher (81.25%) than the sensitivity of ATP detection (62.50%) when analyzing SF directly. The sensitivity of the methods significantly improved (to 94.12%) with SF pre-cultivation. Importantly, both methods provided results in 3–4 h when analyzing SF directly, while results from pre-cultivated SF were obtained 19–20 h after sample collection. Our results suggest that bacteriophage-based methods are specific and sensitive and importantly, faster than standard culturing methods. The addition of new bacteriophages to expand the bacterial detection spectrum could lead to the development of a faster, more sensitive, specific, and also economical, and handy method for PJI diagnosis.