TWAS initiated its affiliateship category for young scientists in 2007. During their five-year tenure, TWAS Young Affiliates are invited to participate in five TWAS general meetings and conferences.

The Academy's Regional Offices are located in Rio de Janeiro, Brazil; Beijing, China; Alexandria, Egypt; Bangalore, India; and Pretoria, South Africa (as of 2015; previously Nairobi, Kenya). Generally, they nominate only one person per country among the five individuals selected each year. To be eligible for selection, researchers must:

• be aged 40 or less on 1 January of the year in which they are selected;
• have been living and working in a developing country for at least the preceding three years;
• have an excellent track record of at least 10 international publications in peer-reviewed journals.

Being selected a TWAS Young Affiliate does not automatically lead to full membership of TWAS. Specifically, TWAS Young Affiliates:

• will be invited to attend all TWAS General Meetings and General Conferences free of charge;
• are entitled to attend TWAS General Meetings as observers, i.e. they will be permitted to participate in the discussions, but will not have any voting rights;
• will be invited to attend regional meetings of TWAS Fellows organized by the Regional Offices;
• will be invited to participate in the activities of TWAS national chapters in their home countries (if such a chapter is active);
• will receive copies of TWAS publications such as the TWAS Newsletter, Year Book, and Annual Report;
• will have their biodata published in an annual Young Affiliate registry, to be made available at each TWAS General Meeting;
• are eligible for TWAS Prizes (unlike TWAS members);
• are encouraged to provide feedback to TWAS on how the Academy can respond to the needs of young scientists in developing countries;
• are encouraged to provide information about TWAS programmes to their students and colleagues;
• are encouraged to seek out and nominate excellent scientists from developing countries, especially science- and technology-lagging countries, for TWAS awards;
• are encouraged to seek out excellent scientists from science- and technology-lagging countries and recommend their nomination for TWAS membership (via a TWAS member).

At the end of the five-year affiliateship period, the status of 'TWAS Young Affiliate' will be changed to 'TWAS Young Alumnus'. TWAS Young Alumni will continue to be encouraged to seek nomination for a relevant TWAS Prize or as a TWAS Fellow; to be kept on the TWAS mailing list and will continue to receive the TWAS Newsletter, e-Bulletin, etc.; to act as a resource person for TWAS. However, a Young Alumnus will no longer be invited to attend TWAS General Meetings or be nominated by TWAS to attend meetings for young scientists organized by other parties.