Complementing the research on immigrants’ exclusion from most U.S. service institutions as well as their “bureaucratic incorporation,” this study examines how and why immigrants’ negotiations with informal barriers vary across institutional contexts. Drawing on 25 in-depth interviews, I compare low-income, monolingual Mexican immigrant mothers’ caretaking experiences across two settings: at schools and in health care facilities. My analysis suggests that different institutional settings place different demands for cultural capital on these women while offering varying opportunities for their usage of “motherhood capital,” resulting in diverse patterns of institutional negotiations. These mothers’ interactions with school personnel feature the experiences of “emergent alliance.” When advocating for their children at healthcare facilities, they report a mixture of “successful confrontations” and “blocked negotiations.” These findings contribute to discussions of immigrant inclusion/exclusion. More broadly speaking, by developing the concept of motherhood capital, the study dialogues with the literatures on cultural capital and political mothering.