Next-generation sequencing (NGS) allows the detection of multiple genetic targets in different tumor types. This study aimed to confirm the benefits of implementing NGS testing in-house for non-small-cell lung cancer (NSCLC) samples in molecular pathology laboratories. A multi-institutional study was conducted to evaluate the analytical performance, turnaround time, and feasibility of in-house NGS testing of 50 genes from 283 NSCLC samples. The first phase was a retrospective study with interlaboratory testing (21 samples), and the second phase was a prospective study with intralaboratory testing (262 samples). The retrospective study showed a 100% sequencing success rate for DNA and RNA, high interlaboratory concordance (95.2%), and a strong correlation (R