Dr. rer. nat. Rajinder Singh is/was member of the following Scientific Societies:
- European Physical Society (2009-2011)
- German Physical Society/History of Physics & Didactic of Physics (1998-...)
- German Soc. Sci. Med. & Tech (2005-2020)
- Scientific Instrument Commission (1998-...)
- Education and Science Union (2005-...)
- European Society for the History of Science (2004-...)
- Astronomical Society (AG-HA)
- "Jugend forscht eV", Hamburg (2005-2019)
- Bulgarian Soc. Chem. Edu. & Hist. & Phil. Chemistry
- Member of Editorial Board - Indian Journal of History of Science (2016-2019), Science and Culture, Kolkata, ISNA, (2015-...), and Scientific Voyage, Kolkata (2018-...)
- Memeber of Selection Committee, Heinrich Boell Foundation (2014-2019).
- Honorary Member of the Society for Promotion of Science and Technology in India (2021-...).