Introduction: Survival after breast cancer is determined by disease related factors such as stage at diagnosis, patient characteristics, e.g., age, and treatment. Aim: To review evidence published during the last ten years on the effect of comorbidity on survival after early breast cancer. Methods: A search in Pubmed with keywords, breast neoplasm, comorbidity, and survival, was performed. A total of 18 studies published between 2000 and August 2010 was included in this review. Results: All 18 studies demonstrated that comorbidity had a significant impact on survival after breast cancer with poorer survival among patients with one or more comorbid conditions. The effect of comorbidity persisted after adjustment for age at diagnosis and stage of disease. Older patients with comorbidity were less likely to receive therapy according to guidelines. Conclusion: Presence of comorbidity at diagnosis is an important prognostic factor in early breast cancer, irrespective of age and stage of disease.