In this paper, we report the multiferroic and piezoelectric behavior observed in transition-metal doped ZnO films. The experimental results indicated that the Co-doped ZnO films deposited by magnetron sputtering possess a Curie temperature higher than 700K, and the magnetic moments of Co are intimatedly correlated to the doping concentration and the substrate. A giant magnetic moment of 6.1 B/Co is observed in (4 at.%) Co-doped ZnO films. Ferroelectric and ferromagnetic behaviors simultaneously were also obtained in V and Cr doped ZnO films on Pt(111)/Ti/SiO2/Si(100) substrates by reactive sputtering method, revealing a multiferroic nature. The high piezoelectric d33 coefficient 80-120 pm/V has also been achieved by Cr and V substitutions, which could make Cr-doped or V-doped ZnO a promising material in piezoelectric devices.