Nursing shortage is an important and multifaceted challenge in the health systems and has reached a warning threshold. The factors associated with nursing shortage vary from country to country. Therefore, this study compared the causes of nursing shortage and suggested strategies to help resolve this concern both in Iran and in the world. To conduct this systematic review, search was done in English and Persian databases from 2000 to 2016. In the preliminary review, 537 articles were included in the study. After reviewing the titles, abstracts, objectives, and results of articles, 32 studies were finalized. The important causes of nursing shortage in the world included aging of the nursing workforce, inadequate admission and training of nurses, aging population, and job abandonment. However, the leading causes in Iran were unwillingness and lack of desire to enter and remain in the nursing field, job abandonment, inadequate salaries, low social status, and negative perception of nursing. Proposed strategies in the world are increasing the salaries, redesigning the work environment, improving the public's perspective, retaining the existing nursing workforce, and flexible work schedules. In Iran, these strategies include increasing salaries and recruitment, enhancing the public's perception of nursing, and supporting nursing organizations. Nursing shortage is a multifaceted concept with varying magnitudes in different countries. Therefore, the strategies to resolve nursing shortage should be based on the unique conditions of each country. The most important strategies to overcome nursing shortage in Iran are focused on the improving the retention of existing nursing workforce.