The term "unmarried" mothers is widely used in South Korea to indicate that carrying a baby without marriage is not culturally acceptable. A societal stigma, which single mothers experience, causes more abortion and doubles the burden of parenting alone. This study aimed to identify what type of information (onset/before pregnancy controllability, offset/after pregnancy ability and effort) contributes to reducing stigmatization toward unmarried mothers. The findings showed that offset effort information has a robust impact on participants' cognitive, affective, and behavioral responses toward mothers of newborns out of wedlock across the three studies (n = 275; n = 266; n = 227, respectively) with different targets (a minor and an adult of 25 years old) and different participants (college students and adults above 30 years old). This pro-effort bias increased behavioral intentions of helping single mothers through the moderators of onset controllability and offset ability and the mediators of cognitive and affective responses. In particular, Study 2 found individual differences, such as type of interpersonal attitude, gender-role attitude, and family communication style moderated the relationship of offset effort with behavioral intentions. Mothers who made an effort to build a better future were ascribed fewer negative stereotypes, evoked more positive emotions, and were considered to deserve more help and support from the public. The findings have implications for communication interventions to lower prejudice against unwed mothers in South Korea. (PsycInfo Database Record (c) 2024 APA, all rights reserved).