NEST has participated or played a pivotal role in institution building in the NGO sector. As a founding member, NEST has contributed to the establishment of the international network, the RING (see Partnerships). And, at the international level also, NEST has been active in the building and working of the NGO  network on combating desertification, RIOD (Reséau International d' ONG sur la desertification).

NEST anchored the attempt by the Commonwealth Foundation to build a Commonwealth Liaison Unit (CLU) in Nigeria in the early 90s, and, with agreement of the Commonwealth Foundation, subsequently applied funds meant for that purpose towards the effort to set up the Nigeria NGO Consultative Forum (NINCOF). NEST managed the additional funding support provided by the Ford Foundation to NINCOF between 1995 and 1997, and was pivotal to the running of NINCOF until December 2000. Other local institutions that NEST has helped in building include the Nigerian Environmental Education Network (NEEN), a Development Information Network (DevNet) and the Nigerian Environment and Development Network (NEDNET).