Objective There is evidence that parents play an important role in their adolescent's health and well-being, but the links between specific daily processes and biological mechanisms relevant to health remain to be determined. In this study, we examined the role of parental accuracythat is, whether parents who are more accurate about their adolescents' daily experiences have adolescents with better psychological functioning and inflammatory regulation. Methods In a 2-week daily diary study of 116 parent-adolescent dyads, we examined whether parental accuracy about their adolescent's daily demands and the positivity of their day together were associated with markers of psychological functioning and with regulation of the inflammatory response in terms of glucocorticoid sensitivity (the extent to which cortisol is able to dampen the production of inflammatory proteins) in adolescents. Results Adolescents whose daily experiences were perceived more accurately by their parents reported better psychological adjustment (lower stress and depression) and a greater sensitivity of their immune cells to anti-inflammatory signals from cortisol (i.e., diminished production of inflammatory proteins when cells were stimulated with the combination of a bacterial product [lipopolysaccharide] and cortisol; || range, 0.38-0.53, all p values <.041). Conclusions Greater parental accuracy regarding adolescents' daily experiences is associated with better adolescent psychological adjustment and a more sensitive anti-inflammatory response to cortisol. These results provide preliminary evidence that parental accuracy regarding their adolescent's daily experiences may be one specific daily parent factor that plays a role in adolescent health and well-being.