A circular collapsible rack for cuvettes and like vessels such as test tubes is disclosed which features a flat base and likewise flat upper and lower vessel support members of a suitable plastic material. The base has a plurality of equally spaced circumferential arms which are bent upward and substantially normal to its bottom via natural hinges. The arms include apertures for receiving tabs on the upper and lower support members, whereby said members are snapped into the base so as to be removably and adjustably supported thereby. With the disclosed arrangement the base and the upper and lower support members may be stored and shipped in the flat state so as to reduce storage space and shipping costs, and the assembled rack may accommodate a variety of vessel quantities and sizes, as is desirable.