Neoproterozoic ( c. 640 Ma) amphibolite facies metamorphism and deformation have been shown recently to have affected the Isbj ø rnhamna and Eimfjellet Complex of Wedel Jarlsberg Land in southwestern Spitsbergen. New SHRIMP zircon U−Pb and in situ electron microprobe monazite and uraninite U−Th−total Pb ages are presented here on a pegmatite occurring within the Isbj ø rnhamna metasedimentary rocks. Although the dated zircons are full of inclusions, have high−U contents and are metamict and hence have experienced notable Pb−loss, the new Cryogenian ages are consistent with the age of regional metamorphism of the host metasediments, providing additional evidence for a clear distinction of the Southwestern Province from the other parts of the Svalbard Caledonides.