Commercial fillers, including carbon black (N550), halloysite nanotubes (HNTs), and precipitated silica, were replaced by recycled poly(ethylene terephthalate) powder (R-PET) in natural rubber (NR) composites. Five different compositions of NR/N550/R-PET, NR/HNTs/R-PET, and NR/silica/R-PET compounds, i.e., 100/20/0, 100/15/5, 100/10/10, 100/5/15, and 100/0/20 parts per hundred rubber (phr), were prepared on a two-roll mill. The curing behavior, tensile properties, and morphological characteristics of the natural rubber composites were investigated. The results indicated that the replacement of carbon black, HNTs, and silica by R-PET decreased the tensile strength and tensile modulus, such that NR/silica/R-PET composites showed the lowest effect, followed by NR/HNTs/R-PET and NR/N550/R-PET composites. The negative effect on these properties can be explained by the decrease of crosslink density. The curing results revealed that with the replacement of carbon black by R-PET, the scorch time and cure time decreased, but that the NR/HNTs/R-PET and NR/silica/R-PET composites exhibited the opposite trend. Scanning electron microscopy investigation of tensile fracture surfaces confirmed that the co-incorporation of N550/R-PET improved the dispersion of R-PET and enhanced the interaction between the fillers and NR matrix more than R-PET and silica/R-PET hybrid fillers. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers