The 21st century arrived with global growth of energy demand caused by population and standard of living increases. In this context, a suitable alternative to produce COx-free H₂ is the catalytic decomposition of methane (CDM), which also allows for obtaining high-value-added carbonaceous nanomaterials (CNMs), such as carbon nanotubes (CNTs). This work presents the results obtained in the co-production of CO_x-free hydrogen and CNTs by CDM using Ni–Cu and Co–Cu catalysts supported on carbon derived from Argan (Argania spinosa) shell (ArDC). The results show that the operation at 900 °C and a feed-ratio CH₄:H₂ = 2 with the Ni–Cu/ArDC catalyst is the most active, producing 3.7 g_C/g_metal after 2 h of reaction (equivalent to average hydrogen productivity of 0.61 g H₂/g_metal∙h). The lower productivity of the Co–Cu/ArDC catalyst (1.4 g_C/g_metal) could be caused by the higher proportion of small metallic NPs (<5 nm) that remain confined inside the micropores of the carbonaceous support, hindering the formation and growth of the CNTs. The TEM and Raman results indicate that the Co–Cu catalyst is able to selectively produce CNTs of high quality at temperatures below 850 °C, attaining the best results at 800 °C. The results obtained in this work also show the elevated potential of Argan residues, as a representative of other lignocellulosic raw materials, in the development of carbonaceous materials and nanomaterials of high added-value.