Our previous study has demonstrated that luteinized granulosa cells (GCs) have the potential to proliferate and that the telomerase activity (TA) of luteinized GCs may predict the clinical outcomes of IVF treatment. However, in the field of telomere research, there have always been different opinions regarding the significance of TA and telomere length (TL). Thus, in the present study, we compared the effects of these two parameters on IVF treatment outcomes in the same individuals. TL did not differ significantly between the pregnant group and the non-pregnant group. The TA, number of retrieved oocytes and rate of blastocyst transfer were significantly higher in the pregnant group than in the non-pregnant group (0.8825 OD×mm, 12.75±2.20 and 34.48%, respectively, in the pregnant group vs 0.513 OD×mm, 11.60±0.93 and 14.89%, respectively, in the non-pregnant group (P<0.05)), while basal FSH level was lower in the pregnant group than in the non-pregnant group. The subjects did not differ with regard to ovarian stimulation or other clinical characteristics. A TA increase of 1 OD×mm increased the chance of becoming pregnant 4.769-fold (odds ratio: 5.769, 95% CI: 1.434-23.212, P<0.014). The areas under the receiver operating characteristic curves were 0.576 for TL and 0.674 for TA (P=0.271 and P<0. 012 respectively). The corresponding cut-off points were 4.470 for TL and 0.650 OD×mm for TA. These results demonstrate that TA is a better predictor of pregnancy outcomes following IVF treatment than TL. No other clinical parameters, including age, baseline FSH level or peak oestradiol level, distinguished between the pregnant group and the non-pregnant group as effectively as TA.