Abstract Mafic dyke complexes within the Scandinavian Caledonides occur as part of the rifted Baltoscandian margin and in exotic terranes derived from outboard of Baltica, Mafic dyke swarms in the Rohkunboni Nappe (Upper AUochthon of Indre Troms) have major and trace element geochemistry with N‐MORB to T‐MORB affinity. Chondrite‐normalized REE patterns are flat to concave and slightly enriched in LREE. The dolentes are characterized by the following trace and REE ratios: La/Yb = 0.98–1.84, La/Sm = 0.59–0.97, Zr/Y = 2.88–4.55, Zr/Nb = 3.71–6.8, and Ce/Yb = 0.44–0.93. With regard to general geochemical traits, the Rohkunborri mafic dykes compare with MORB. Some samples have island arc and volcanic arc affinity; however, they lack the prominent negative Nb anomaly typical of island arc basalts. REE patterns and (La/Sm)ch versus (La/Yb)ch covariance compare excellently with that of Tertiary T‐MORB of the northeastern Atlantic margin (V⊘ring Plateau). Based on geochemistry, structural setting and preliminary geochronological results, the mafic dykes are interpreted to have intruded an extensively thinned Baltoscandian passive margin in latest Proterozoic to earliest Phanerozoic time. The dyke swarms are correlated with those of the Sarektjåkkå Nappe, the Kebne Dyke Complex and the Vaiwan‐cohkka Nappe within the Seve Nappe Complex in northernmost Sweden and the Corrovarre Nappe of the Middle Allochthon in northern Troms, Norway. St⊘len, L.K., 1994: Derivation of mafic dyke swarms in the Rohkunborri Nappe, Indre Troms, northern Norwegian Caledonides: Geochemical constraints. GFF, Vol. 116 (Pt. 3, September), pp. 121–131. Stockholm. ISSN 1103–5897.