Maternity protection is a normative fundamental human right that enables women to combine their productive and reproductive roles, including breastfeeding. The aim of this study is to examine the uptake of Vietnam’s maternity protection policy in terms of entitlements and awareness, perceptions, and gaps in implementation through the lens of formally employed women. In this mixed methods study, we interviewed 494 formally employed female workers, among whom 107 were pregnant and 387 were mothers of infants and conducted in-depth interviews with a subset of these women (n = 39). Of the 494 women interviewed, 268 (54.3%) were working in blue-collar jobs and more than 90% were contributing to the public social insurance fund. Among the 387 mothers on paid maternity leave, 51 (13.2%) did not receive cash entitlements during their leave. Among the 182 mothers with infants aged 6–11 months, 30 (16.5%) returned to work before accruing 180 days of maternity leave. Of 121 women who had returned to work, 26 (21.5%) did not receive a one-hour paid break every day to express breastmilk, relax, or breastfeed, and 46 (38.0%) worked the same or more hours per day than before maternity leave. Although most women perceived maternity leave as beneficial for the child’s health (92.5%), mother’s health (91.5%), family (86.2%), and society (90.7%), fewer women perceived it as beneficial for their income (59.5%), career (46.4%), and employers (30.4%). Not all formally employed women were aware of their maternity protection rights: women were more likely to mention the six-month paid maternity leave (78.7%) and one-hour nursing break (62.3%) than the other nine entitlements (2.0–35.0%). In-depth interviews with pregnant women and mothers of infants supported findings from the quantitative survey. In conclusion, although Vietnam’s maternity protection policy helps protect the rights of women and children, our study identified implementation gaps that limit its effectiveness. To ensure that all women and their families can fully benefit from maternity protection, there is a need to increase awareness of the full set of maternity entitlements, strengthen enforcement of existing policies, and expand entitlements to the informal sector.