The mothers-adolescent discussion regarding sexual and reproductive health (SHR) issues plays an important role in preventing negative outcome associated with sexual risk behaviors. The present study aimed to explore the relationship between mothers' competence and comfort in SHR discourse with adolescent girls and its related factors. A cross-sectional study was conducted involving 160 mothers from July to September 2020. Data were collected through questionnaires covering demographic characteristics, Mother's Comfort in Sexual Discourse (MCSD), Mother's Interest in Sexual Discourse (MISD), and Parenting Sense of Competence (PSOC). The collected data were analyzed using simple and multiple linear regression models. The mean scores for MCSD, MISD, and PSOC were 45.49±16.15 (13-78), 7.9±4.2 (0-13), and 64.07±9.44 (45-94), respectively. The primary topics of mother-adolescent discourse on SRH were menstruation (5.61±0.98) and the delivery process (4.55±1.57). The mean age for "sex talks" and age-appropriate "sex talks" with daughters was 11.76±1.85 (range: 6-15) and 17.05±1.86 (range: 14-23) years, respectively. Significant associations were found between MCSD and MISD (β=0.482, p<0.0001), PSOC (β=0.223, p<0.005), self-efficacy (β=0.202, p<0.011), mother's job (β=0.185, p<0.019), mother's education (β=0.173, p<0.029), and father's age (β=0.161, p<0.042). After adjusting for other variables, major influencing factors on MCSD included MISD (β=0.487, p<0.0001), self-efficacy (β=0.143, p<0.039), satisfaction (β=0.169, p<0.015), daughter number (β=-0.235, p<0.014), son number (β=-0.219, p<0.024), birth rank (β=0.263, p<0.008), and residency (β=0.172, p<0.014). MISD, PSOC, and certain demographic characteristics emerge as significant factors influencing MCSD in mother-daughter sexual discourse. As such, it is imperative to consider these determinants when devising strategies to maintain and enhance the sexual health of teenage girls.