Herein, for the first time mesostructured 3D self-assembled β-Ni(OH)₂ clusters with high surface area, large pore size, and uniform flower-like morphology have been synthesized by implementing a novel microwave heating method, using glycine as the cappant. The β-Ni(OH)₂ clusters are subjected to aqueous phase pollutant adsorption for multiple anionic dyes [congo red (CR), acid fuchsin (AF) and acid red 27 (AR-27)], and heavy metal ions [divalent lead ion, Pb(II) and divalent cadmium ion, Cd(II)]. The comprehensive kinetic analyses show that the adsorption of dyes and metal ions on the β-Ni(OH)₂ cluster surface occurs by chemisorption (pseudo-second order kinetics) and intraparticle diffusion (film and pore diffusion) processes. Further, the β-Ni(OH)₂ clusters show excellent equilibrium adsorption capacity for all the anionic dyes and metal ions. The equilibrium isotherm data show homogenous distribution of CR and AF dyes, and heterogeneous distribution of AR-27 dye on the β-Ni(OH)₂ surface. The excellent adsorption efficiency is attributed to the microwave-induced highly hydroxylated rippled 2D surface, open pore architecture, and suitable pore distribution of the β-Ni(OH)₂ clusters, which collectively cause strong hydrogen bonding between the cluster surface and anionic dyes as well as metal ions.