Hospitalized patients on mechanical ventilation are at high-risk of developing ventilator-associated pneumonia (VAP), making early and accurate diagnosis essential for the best possible treatment outcomes. This review examined various laboratory techniques, such as aerobic cultures, Gram’s stain, and molecular techniques, to assess how well they diagnose VAP.  We have done search strategies using Google Scholar, Medline Complete, and PubMed. Extensive statistical tools were utilized to examine studies and evaluate the diagnostic accuracy of laboratory results. Multiplex PCR was superior to Gram’s stain and culture methods in terms of sensitivity (92%) and specificity (86%). On the other hand, Gram’s stain showed the highest specificity (78.9%) and the lowest sensitivity (74.6%). The results of semi-quantitative, quantitative, enrichment culture showed a lower specificity (75.97%) but a moderate sensitivity (78.5%). The most accurate diagnostic approach for VAP, according to a meta-analysis, was multiplex PCR-based testing, closely followed by culture methods. Beyond separate tests, multiplex PCR, culture, and Gram’s stain combination increased sensitivity. Prompt and precise VAP diagnosis is essential for efficient treatment. With possible improvements through combination diagnostic techniques, multiplex PCR remains the most accurate diagnostic tool. However, more investigation is necessary to improve and certify VAP diagnostic instruments.