This paper, for the first time, proposed a novel eye-diagram estimation method for pulse amplitude modulation with N-level (PAM-N) signaling. For verification, a through-silicon via (TSV) channel was fabricated. Because the input of the proposed method is an insertion loss, the loss of the fabricated TSV channel was measured up to 110 GHz. The estimated eye diagrams and measured eye diagrams were compared for the same TSV channel. The proposed method and measurements have nearly the same eye-height and eye-width values at data rates of 2, 4, and 8 Gb/s. Therefore, the proposed method successfully provides PAM-N's eye diagram with the insertion loss. Furthermore, bathtub curves were compared for the proposed method and measurements. The proposed method provides a bathtub curve up to 10–12, but in contrast, the measurements only provide a bathtub curve up to 10–5 due to a limited number of samples. Both of the bathtub curves are nearly the same up to 10–5 in amplitude. In conclusion, the eye-diagram estimation method for PAM-N signaling is successfully proposed and verified.