Big Brothers Big Sisters

Updated: Jan 02, 2023
Evidence Rating:
Suggestive Tier


  • Program:

    A community-based mentoring program for disadvantaged youth.

  • Evaluation Methods:

    Two well-conducted randomized controlled trials (RCTs), each with a multi-state sample of over 1,000 youths averaging 12 years of age.

  • Key Findings:

    Both RCTs found sizable reductions in substance use and types of misconduct over an 18-month follow-up period, based on youth and/or parent report.

  • Other:

    Study limitations include reliance on youth and parent reports to measure outcomes without corroboration through more objective measures, and a follow-up period of only 18 months. One of the RCTs is ongoing and plans to address these limitations by measuring official arrest rates over a four-year follow-up period.

[Disclosure: Arnold Ventures provided funding for one of the two RCTs (Dubois, Herrera,]

Big Brothers Big Sisters of America is the largest mentoring organization in the United States, with over 230 agencies serving more than 100,000 youth nationwide in 2020. Community-Based Mentoring is the organization’s flagship program. The program matches youth ages 6 to 18, predominantly from low-income households, with adult volunteer mentors.

The youth’s parent(s)/guardian(s) apply for the youth to be matched with a mentor through a written application and youth/parent interview. Potential mentors are screened by a Big Brothers Big Sisters caseworker through a personal interview, home visit, and criminal, background, and reference check to ensure that they are not a safety risk and are likely to form a positive relationship with the youth. Prior to a match being made, the youth and parent meet with the potential mentor; the match’s completion requires parental approval.

The mentor and youth typically meet for 2 to 4 times per month for at least a year, and engage in activities of their choosing (e.g. studying, cooking, playing sports). The typical meeting lasts 3 to 4 hours.

For the first year, Big Brothers Big Sisters staff maintain monthly contact with the mentor, as well as the youth and their parent, to ensure a positive mentor-youth match, and to help resolve any problems in the relationship. Mentors are encouraged to form a supportive friendship with the youth, and not seek to modify the youth’s behavior or character.

The Washington State Institute for Public Policy (2019) has estimated the cost per youth for a year of services in the Community-Based Mentoring program at $1,765.

Click here for the Big Brothers Big Sisters website.

To see our full evidence summary:
Download PDF


Dubois, David L., Carla Herrera, Julius Rivera, Vanessa Brechling, and Staci Root, “Randomized Controlled Trial of the Effects of the Big Brothers Big Sisters Community-Based Mentoring Program on Crime and Delinquency: Interim Report of Findings,” 2022, linked here.

Grossman, Jean Baldwin and Joseph P. Tierney, “Does Mentoring Work? An Impact Study of the Big Brothers Big Sisters Program.” Evaluation Review, Vol. 22, No. 3, June 1998, pp 403-426, linked here.

Tierney, Joseph P., and Jean Baldwin Grossman, “Making a Difference: An Impact Study of Big Brothers Big Sisters.” Public/Private Ventures, 1995 (reprinted 2000), linked here.

Washington State Institute for Public Policy, Mentoring: Big Brothers Big Sisters Community-Based (taxpayer costs only), 2019. (Big Brothers Big Sisters website)