The prediction of unfavorable long-term esthetic outcome (AO) is important for patient consultation. We aimed to analyze variables characterizing the improvement and impairment of AO over time after breast-conserving surgery. A subgroup of a prospective, monocenter cohort study was analyzed to evaluate the results of the BCCT.core software (Breast Cancer Conservative Treatment.cosmetic results) which was used to objectively assess the AO before (n = 356), shortly after (n = 294) and in median 3 years after surgery (n = 356). We analyzed potential influencing factors (such as body mass index, (y)pT-stage, weight of resected specimen, etc.) on the AO using logistic regression analyses (n = 256). Finally, we tried to characterize groups of patients with improving or impaired AO over time (n = 294). Predictors for an unfavorable AO were an axillary lymphadenectomy (OR = 4.05), a tumor in the 12 o'clock position (OR = 2.22), a tumor stage larger or equal to (y)pT2 stage (OR = 2.11), and a surgical specimen weight >75 g (OR = 2.71). Patients with lower specimen weight were more likely to improve in the long-term follow-up (p = 0.018), whereas patients with a higher (y)pT-stage tended to become impaired with time. Although overall AO decreased over time, nearly half of the patients with an unfavorable AO shortly after surgery improved in the long-term follow-up. Predictors of unfavorable AO can be used in patient consultation preoperatively to prepare them for the postsurgical period and/or to recommend surgical alternatives (e.g., more complex oncoplastic techniques). Knowledge of improvement and impairment may help patients and physicians in the postsurgical consultation setting.