Patient-reported outcomes (PROs) associated with insulin therapy are potentially important determinants of adherence to diabetes management programs. This article reviews published evidence of PROs over the past 3 decades in patients with type 1 diabetes (T1D) and/or type 2 diabetes (T2D) who used vial and syringe for insulin delivery compared to those who used insulin pens. Based on predetermined selection criteria, articles were identified through a search of primary sources published from January 1980 to February 2008. Two independent reviewers determined study eligibility and performed a detailed evaluation of the articles that met the selection criteria. Of the 124 articles screened, 41 met selection criteria. Approximately 75% of the selected articles were published between 1990 and 2008, and a majority (78%) of the research studies was conducted outside the United States. Most (>75%) of the studies evaluated male and female patients with T1D and/or T2D and mean ages around 45 years. Studies used varied comparative study designs with follow-up periods ranging from 2 weeks to 5 years. The PROs assessed in these articles included preference, acceptability, treatment satisfaction, ease of use, convenience, injection pain, handling, and dosing. Most articles (n = 36) showed more favorable PROs for insulin pen users compared to vial and syringe users. These findings have potential clinical and policy implications for patients, diabetes care providers, and/or payers to make evidence-based decisions regarding ways to facilitate initiation and management of insulin therapy.