We followed 402 African American young adults from ages 24 to 29, a period of emerging committed relationships, to examine the association of contextual stress (CS), for example, experiences of financial strain, victimization, and racial discrimination, with inflammation, and to test predictions that greater perceived relationship warmth and support (PRWS) at age 29 would moderate the association between earlier CS and inflammation, using a multiplex assessment of cytokines to construct an index of the ratio between predominantly proinflammatory cytokines versus predominantly anti-inflammatory cytokines. CS experienced at age 24 was associated with greater inflammation at age 29 in the full sample (b = .112, p = .004). PRWS at age 29 moderated the association of earlier CS with inflammation (b = -.114, p = .011), but there was no significant main effect of PRWS (b = -.053, p = .265). Finally, using an internal moderator approach, we compared the association of CS with inflammation among those not in a committed relationship to those in more or less supportive relationships, showing a significant and stronger association of CS with inflammation for those with low PRWS (-1 SD; b = .182, p < .001), a weaker and nonsignificant association of CS with inflammation among those with higher PRWS (+1 SD; b = -.002, p = .975), and an intermediate and nonsignificant association of CS with inflammation among those with no committed romantic relationship (b = .077, p = .227). Results were robust to number of cytokines included in the inflammation index. (PsycINFO Database Record (c) 2019 APA, all rights reserved).