Purpose. How can charities best increase the donations to their causes? This study aims to answer this question by synthesizing review-level evidence for increasing charitable giving.Methodology. This paper is an umbrella review of systematic reviews on interventions that influence financial donations to non-profits.Findings. We found 14 meta-analyses (combined N = 1,510,966) covering nine factors influencing charitable giving. Three factors increased donations: tax deductibility, encouraging women to make intuitive judgements, and legitimizing paltry contributions. Two factors reduced donations: compassion fade and larger starting amounts of money. Four factors did not influence donations: ‘door-in-the-face’, prosocial media, government crowding out/in, and artificial surveillance cues. Most reviews focused on contrived experiments measuring one-off donations, such as dictator games. None met all best-practice guidelines for systematic reviews.Practical implications. To increase donations, charities could promote the tax deductibility of the donation, the effects of even small contributions, and highlight the impact of the donation. Systematic reviews allow for more robust conclusions, but many recent reviews of philanthropy marketing neglect best-practice and focus on topics of limited applied utility.