A serpentinite-matrix melange complex with blocks of greenschist, blueschist, metagabbro, orthogneiss, amphibolite and eclogite is present within a small structural window beneath Upper Triassic ophiolite about 2 km north of Puerto Nuevo in the central Vizcaine Peninsula. The melange complex consists of three units: lower (more then 200 m thick) and upper (less than 100 m thick) serpentinite breccia units and the intervening exotic block unit (less than 100 m thick). The tectonic contact of the complex with the serpentinized (mainly chrysotile-bearing) basal harzburgite unit of the ophiolite is gradational and subparallel to the ophiolite stratigraphy; rocks below the melange complex are not exposed. The melange complex probably represents a thrust fault within the basal ultramafic part of the Sierra de San Andres ophiolite. The exotic metamorphic rocks are inferred to have been dragged up from one or more underlying metamorphosed ocean-floor and volcanic-arc terranes. Metamorphism, composition, lithology, tectonic position, and preliminary age data argue the Puerto Nuevo melange should not be correlated with the melange complexes on Cedros and the San Benitos Islands nor with the melanges of the Franciscan Complex of Alta California. The Puerto Nuevo melange is instead interpreted as an older, more inboard, blueschist-bearing unit analogous to the blueschist units of the Klamath and Dierra Nevada Mountains. The multiplicity of subduction-zone complexes, ophiolites, and volcanic-arc sequences suggests that the Vizcaino Peninsula region is composed of a collage of tectonostratigraphic terranes that may be allochthonous relative to each other and the North American craton.