Relative motions between the Pacific plate (P), Indo-Australian plate (IA), New Hebrides (NH) arc microplate and the North Fiji Basin (NFB) microplate are estimated using shallow seismicity, 276 focal mechanism solutions, bathymetry, magnetism and the RM-2 plate model of Minster and Jordan (1978). Within the NFB, we define the western NFB (WNFB), eastern NFB (ENFB) and southern NFB (SNFB) microplates. A 8 cm/y spreading in a N72°E direction occurs along the N-S trending spreading ridge of NFB (WNFB-ENFB boundary). Along the ENFB-IA boundary located at 176°E, a 3 cm/y extension in a N108°E direction is proposed. The WNFB-P boundary which includes the Hazel Holme Extensional Zone (HHEZ), is complex and a general N25° E extension (2 cm/y) is inferred. The Fiji fracture zone (FFZ) is composed of two segments: Along the eastern zone (P-IA boundary) trending N80° E, a left-lateral strike-slip motion occurs (9.6 cm/y) accommodated by minor N109°E extension (pull-apart); while along the western zone (ENFB-P boundary) a N84°E trending left-lateral strike-slip motion (7 cm/y) is inferred. The WNFB-SNFB boundary corresponds to a N70° E broad fracture zone along which an E-W left-lateral strike-slip motion is proposed. The SNFB microplate moves rapidly eastwards (10.5 cm/y at 172°E) and is almost attached to the IA plate. Within the NFB, an improved model is discussed which includes deformations within the IA and P plates and rotations with Euler poles close to the NFB. Along the New Hebrides trench, the consumption rates are respectively 16, 15, 9 and 12 cm/y at 11°, 12.5°, 15.5° and 20°S. The minimum rate occurs where the d'Entrecasteaux ridge collides with the New Hebrides arc. Rates of extension at the rear of the NH arc are 7, 5.5 and 2 cm/y at 11°, 12.5° and 20°S respectively. Back-arc compression occurs between 13°30′S and 17°S. The western end of the Hazel Holme extension zone coincides with the 13°30′S boundary separating the NH back-arc compressive belt and the northern NH back-arc troughs. South of 21°–22° S the trend of the slip vector changes along the NH trench from N70°E to N20°W. This implies a N-S motion of convergence along the E-W trending southern part of the NH trench (motion SNFB-IA of 1.5 cm/y at 172°E) and the existence of a N70° E trending left-lateral fracture zone crossing the southern part of the NFB. This fracture should be considered as a major plate boundary.