We have previously reported Hi-Plex, a multiplex PCR methodology for building targeted DNA sequencing libraries that offers a low-cost protocol compatible with high-throughput processing. Here, we detail an improved protocol, Hi-Plex2, that more effectively enables the robust construction of small-to-medium panel-size libraries while maintaining low cost, simplicity and accuracy benefits of the Hi-Plex platform. Hi-Plex2 was applied to three panels, comprising 291, 740 and 1193 amplicons, targeting genes associated with risk for breast and/or colon cancer. We show substantial reduction of off-target amplification to enable library construction for small-to-medium-sized design panels not possible using the previous Hi-Plex chemistry.