The efficient delivery of bioactive compounds into cells is a major challenge in drug discovery. We report herein the development of novel methods for intracellular delivery of functional proteins (including antibodies) and native small-molecule drugs by making use of cell-penetrating poly(disulfide)s (CPDs). CPDs were recently shown to be rapidly taken up by mammalian cells in endocytosis-independent pathways, but their applications for delivery of proteins and native small-molecule drugs have not been demonstrated. With our newly developed, CPD-assisted approaches, rapid and "bioorthogonal" loading of cargos was carried out with pre-synthesized CPDs, in two steps and in a matter of minutes under aqueous conditions. The resulting CPD-cargo conjugates were used immediately for subsequent cell delivery studies. With the versatility and flexibility of these methods, we further showed that they could be used for immediate delivery of a variety of functional cargos with minimum chemical and genetic manipulations. The minimal cell cytotoxicity of these CPDs and their cargo-loaded conjugates further highlights the unique advantage of this new cell-transduction method over other existing strategies and ensures that our entire delivery protocol is compatible with subsequent live-cell experiments and biological studies.