The exploitation of high‐performance nonlinear optical (NLO) materials is necessitated by the broad application of ultra‐intensive and ultra‐fast lasers. The superb nonlinear absorption and electronic‐structure‐related NLO response of M3HHTP2 are introduced here, where M is Co(II), Ni(II), or Cu(II) and HHTP is 2,3,6,7,10,11‐hexahydroxytriphenylene. With the laser excitation at 532 nm, the Cu3HHTP2 exhibits a two‐photon absorption (2PA) cross‐section of 1.38 ± 0.11 × 107 GM, a value much larger than those of most reported NLO materials so far. The NLO response of M3HHTP2 correlates strongly with the number of metal d electrons. With metal d electrons number increasing from 7 to 10, the optical nonlinearity of M3HHTP2 under the laser excitation at 532 nm varies from three‐photon absorption (3PA) in Co3HHTP2, a combination of 3PA and 2PA in Ni3HHTP2, to 2PA in Cu3HHTP2. Abundant metal d electrons can mitigate the ground‐state depletion, and therefore the 2PA is enhanced. Accordingly, the superb nonlinear absorption of Cu3HHTP2 can be associated with abundant d electrons in Cu.