Large-size and high-quality (1−x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 [PZNT(1−x)/x] single crystals (PZNT95/5, PZNT91/9, and PZNT85/15) were grown by a modified Bridgman method using an allomeric 0.69Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 (PMNT69/31) single crystal as a seed. At room temperature, dielectric constant and loss tangent are about 1890 and 0.0692, 4710 and 0.0191, and 673 and 0.0320 for PZNT95/5, PZNT91/9, and PZNT85/15 crystals measured at 100 Hz, respectively. These crystals exhibit high pyroelectric coefficients of 458, 1713, and 460 μC/K m2 for PZNT95/5, PZNT91/9, and PZNT85/15 crystals, respectively. The calculated detectivity and voltage responsivity figures of merit Fd and Fv exceed 5.27, 23.63, and 13.14 μPa−1/2, and 0.0106, 0.0162, and 0.0302 m2/C for PZNT95/5, PZNT91/9, and PZNT85/15 crystals, respectively, over the frequency range of 40–2000 Hz. However, Fd and Fv increase greatly over the temperature range measured. It is needed to improve temperature stability and voltage responsivity to meet the requirements of practical applications. Such investigation reveals that superior pyroelectric performance makes PZNT single crystals promising candidates for infrared detectors and other pyroelectric applications.