A series of polyethylenimine conjugates of single-walled carbon nanotube (PEI-SWNT) containing bioreducible disulfide bonds was synthesized and evaluated for their transfection efficiency. Different molecular weights of polyethylenimine (PEI) were thiolated with different mole ratio of 2-iminothiolane (2-IT). Single-walled carbon nanotube (SWNT) was first carboxylated and then three different cysteine-functionalized SWNT formulations were synthesized via introduced linkers: a) carbonyl group b) spermidine c) 1,8-diamino 3,6-dioxo octane. The final nanocarriers were fabricated upon conjugation of thiolated PEIs and thiolated SWNT via oxidative disulfide bond formation. All PEI-disulfide-SWNT conjugates were capable of DNA condensation and showed improved viability and transfection efficiency compared to PEI itself. Transfection efficiencies were up to 1500 times greater than PEI 25 kDa (C/P = 0.8). The results of this study suggest that the synthesized formulations based on SWNT-CO-Cysteine and PEI 1.8 kDa were the most efficient carriers. Considering the decreased cytotoxicity and higher transfection levels, the conjugates bear the potential for effective delivery of genetic materials.