Using the J2 deformation theory of plasticity, three-dimensional (3-D) elastic-plastic finite element analyses are performed to study the crack-front constraint in finite-sized thin plates under large-scale yielding. Two fracture specimens, center-cracked plate (CCP) and single edge-notched bend specimen (SENB), are modeled, which represent a low and a high constraint geometry, respectively. Numerically determined stress fields near the crack front are compared with those from the HRR field and the JA2 three-term solution. Results show that the in-plane stress fields near the crack front for various applied loads possess the plane strain nature throughout the thickness except in the region near the free surfaces, and can be characterized by the three-term solution within the region of interest, 1 < r /(J / σ0) < 5. In the area near the free surfaces, the crack-front field approaches the plane stress state if the plastic zone size is close to or greater than the plate thickness. The transition of the stress field from the far field, in the plane stress state, to the near crack-front field, dominated by the plane strain state, is demonstrated by the iso-contours of the effective stress. Variations of the J-integral and the constraint parameter A2 along the crack front are also investigated for the two specimens.