The thiol-substituted B-12-cluster mercaptoundecahydro-closo-dodecaborate Na-2[B12H11SH] (BSH) was successfully attached to a poly(amido)amine (PAMAM) dendrimer, which contains a bis(decyloxy)decane core. The physical modification of single-walled carbon nanotubes (SWCNTs) with dendrimer(SB12)(4) afforded a SWCNT/dendrimer(SB12)(4) nanohybrid that exhibited NIR-I-to-NIR-II fluorescence. Herein, we describe a promising strategy for in vivo imaging of boron clusters that may be widely applicable to boron neutron capture therapy.