BackgroundPostpartum sexual concerns are associated with depressive symptoms, distress, and lower relationship satisfaction, and are commonly reported by both mothers and their partners. Previous studies have examined changes in postpartum sexual concern using aggregate scores and have not examined patterns of change for unique concerns, thus ignoring that the initial levels and trajectories of a variety of distinct, postpartum sexual concerns may differ from one another and may differ between mothers and partners. AimsThe aims of the current study were to (i) examine how a variety of postpartum sexual concerns change from 3 to 12 months postpartum for mothers and their partners using a sample of first-time parents, and (ii) examine how mothers and their partners may differ in their initial levels and subsequent changes in postpartum sexual concerns. MethodsFirst-time mothers and their partners (N = 203 couples) independently completed a measure of 21 postpartum sexual concerns at 3, 6, 9, and 12 months postpartum. OutcomesPostpartum Sexual Concerns Questionnaire ResultsGrowth modeling indicated that twelve of mothers’ and 6 of partners’ postpartum sexual concerns declined over time from 3 to 12 months postpartum, only one concern of mothers’ and none of partners’ concerns increased over time, and the remaining 8 and 15 concerns were stable for mothers and partners, respectively. At 3 months postpartum, mothers had higher levels of 11 postpartum sexual concerns than partners, while partners had higher levels than mothers on 4 concerns. Compared to partners, from 3 to 12 months postpartum, mothers showed both steeper decreases in concern about body image changes and steeper increases in concern about returning to work. Clinical ImplicationsVarious postpartum sexual concerns do not all follow the same pattern of change over time, and mothers and their partners share similarities and differences in these patterns. Clinicians should use a checklist to discuss a range of postpartum sexual concerns with both new mothers and their partners. Strengths and LimitationsThis is the first study, to our knowledge, to examine how a variety of postpartum sexual concerns change over time and how mothers and partners both differ and are similar in their experiences. Most couples were in mixed-sex relationships, identified as White, and were relatively affluent; results may not generalize. ConclusionA variety of postpartum sexual concerns follow different patterns of change from 3 to 12 months postpartum, and mothers and partners share similarities and differences in these patterns.Allsop DB, Impett EA, Vannier SA, et al. Change in 21 Sexual Concerns of New Parents From Three to Twelve Months Postpartum: Similarities and Differences between Mothers and Partners. J Sex Med 2022;19:1366–1377.