Background: Many predictors of stress urinary incontinence (SUI) during pregnancy have been investigated. However, no studies have specifically identified a cutoff for pelvic floor muscle (PFM) strength and associated factors that could predict SUI during pregnancy. The aim of this study was to identify the cutoff between PFM strength and SUI, late in the third trimester of pregnancy and associated factors in Indonesian women. Methods: A cross-sectional study was conducted involving 142 women with a pregnancy of 36–40 weeks of gestational age at the Obstetrics and Gynecology clinic of Tebet Subdistrict Hospital, Jakarta, Indonesia. The data were collected through a medical interview, Questionnaire for Urinary Incontinence Diagnosis, physical examination, perineometer, and cough test. Results: SUI was identified in 54.2% of the 142 women. PFM strength 25.5 cmH2O and estimated fetal weight (EFW) ³3,100 g were the factors with the greatest influence on SUI (odds ratio (OR) = 2.52, p = 0.021, and OR = 3.34, p = 0.001, respectively). For women with PFM strength £25.5 cmH2O and EFW ³3,100 g, the prediction for SUI was ~75.39%. Conclusion: Weakening of the PFMs and EFW influence SUI. The cutoff values identified for both variables may be helpful for predicting SUI late in pregnancy.